The westbound District Line train bound for Richmond and Chiswick comes to a halt at Westminster station. Two people board the train and introduce themselves to the other passengers as Mycroft Holmes of Her Majesty’s Foreign and Commonwealth Office and his associate Bernice Summerfield. They take their seats and Bernice asks Mycroft why he did that, but he tells her announcing yourself is the correct protocol when boarding an Underground train. He adds that it would’ve raised suspicion had he not done so, in the same way that her anachronistic reference to the 21st century just did. Bernice says she’d always thought of the London Underground as being a creation of the 20th century, yet here she is in 1893 and it’s already been in existence for 30 years. They’re rushing to prevent an atrocity and although Bernice was hoping their quarry wouldn’t strike again, Mycroft thinks they’re already too late…

On behalf of the Straxus Imperial auction house, Lord Straxus welcomes everyone to the Langham Hotel. He says there’ll shortly be a variety of exclusive items for sale, all of them treasures from the ancient world and of a quality and rarity unmatched at any other private auction. He and his young assistant Septimus have travelled to Egypt, Ceylon and South America to collect these objects and there’ll be a 7-page article describing them in detail in the next edition of “The Strand” magazine. He invites the potential bidders to take their places and adds that they’re free to grab his attention at the after-sales drinks if they think there are any particular items he might be able to acquire for them.

7 May 1893. It’s been a long time since Bernice wrote anything in her diary, but now she thinks it would be a good idea to get some order to her thoughts. She feels like her life isn’t happening in the right order and she’s spent the last month in a place 647 years before she was even born. She and Mycroft have just got back from the scene of a murder - a woman stabbed seven times in the chest. The body was found outside a house on the Richmond High Road which bore the number 77 (and incidentally the Earl of Richmond was King Henry VII of England) and someone had painted a large number seven in Roman Numerals across the front of the house. There had been previous crimes which had been branded with the same number, so it’s obviously all the work of the same man. Mycroft had earlier received a hand-written note consisting purely of the number seven repeated over and over, which offered 77 Richmond High Road as the return address. They knew they’d be too late to stop the murder, but the perpetrator obviously wanted them to see his handiwork. She casts her mind back to when she was heading home from prehistoric Earth and travelling by Time Ring. Peter had already been sent back by the Worm and she was on her way to join him aboard the ship they now call home when her materialisation was disrupted…

Regents Park Zoo is preparing to close down at the end of a routine day and the zookeeper is rounding up the last remaining visitors when he stumbles across what he thinks is a boy lying asleep in the grass. He wakes the ‘boy’ up only to discover it’s Bernice. She appears groggy and confused and asks where she is. When she realises she’s on Earth she begins to panic about her missing son, but the zookeeper assumes she’s drunk and asks her to leave. After she‘s gone, the zookeeper is approached by another stranger - a man who criticises Bernice for being a “modern woman” with short hair and wearing men’s clothes. He regards her as a disgrace and says she needs taking in hand. The zookeeper asks the man to leave as it’s just gone 7 o’clock, but then the man suddenly kills him with a single blow from a knife and drags the body into the bushes where it can’t be seen.

Bernice soon discovers from a discarded newspaper that she’s in the year 1893. She realises Peter must be safe and sound back on their ship in the 27th century, but she needs to get back to him and her Time Ring is no longer working for some reason. She’s not surprised after everything that’s happened to her, but it means she’ll have to think of an alternative solution to her problem.

Later, Bernice arrives at the Diogenes Club and claims to have an urgent message for the attention of Mr Mycroft Holmes. He agrees to meet her, but warns her that her presence here will not be appreciated by the other patrons as women aren‘t allowed inside. When she tells him the message came from Sigerson he knows she’s lying as Sigerson has very particular rules about how he contacts Mycroft. He orders her to leave immediately, but she says the weather outside is like something on Menaxus. She tells him she was a one-time associate of his brother’s and when that doesn’t work, she decides to be blunt and tells him she’s a traveller and the only people she knows in this city are Mycroft’s brother Sherlock and Dr Watson. She’s already been to Baker Street and discovered that Sherlock is dead, so Mrs Hudson directed her to Watson’s surgery. When she got there Dr Anstruther told her Watson was out of the country on a recuperative cruise with his wife. The only remaining option open to her was to find Mycroft. He challenges her on her flippant attitude to his brother’s death, but she points out that Sherlock is only pretending to be dead and he faked the dive off Reichenbach Falls so he could work undercover. Sigerson is actually Sherlock Holmes’s alias, which he uses for contacting Mycroft in secret, and she’s the only person, apart from the two brothers themselves, who knows about it. Bernice invites Mycroft to apply his mastery of observational method to work out who she is and he concludes there can only be one possible answer - she must be Professor Bernice Summerfield.

Mycroft Holmes, the cleverest man in London and someone who’d been described more than once as integral to the functioning of the Victorian state, agrees to take Bernice under his wing. He takes her back to his rooms in Pall Mall, not far from the Diogenes Club, whereupon his housekeeper, Mrs Gross, runs her a bath and prepares some food. Fortunately Mycroft is too old and respectable to be the subject of any social scandals. He tells Bernice it was Dr Watson’s own writing that enabled him to confirm her identity. She mentioned Menaxus back at the Club and he’d seen the name before in the original hand-written manuscript of Watson’s book “All-Consuming Fire“. The manuscript contains several pages of Bernice’s diary and Mycroft recognised the same verbal patterns and idioms. Unfortunately Bernice doesn’t know how she got here, which this makes it impossible for Mycroft to propose a strategy for getting her back. She shows him her Time Ring, but he finds the idea preposterous and because it’s malfunctioning she can’t demonstrate how it works.

They talk for the rest of the evening and Mycroft entertains Bernice with a range of interesting anecdotes and stories. When Bernice becomes tired he suggests she retire to the guest room while he attends to some work of his own. The next morning they meet over the breakfast table where Bernice seems to have finished off the biggest breakfast ever cooked in human history. Mycroft has just returned from Whitehall where he was engaged in matters of Empire. She’s been thinking about her situation and tells him there are people who monitor and observe the shape of time. Even though she knows it’s risky, she proposes attracting their attention somehow by interfering with the patterns of history. They discuss some minor disruptions that won’t cause too much damage but will be noticed by the powers-that-be, but then Mycroft says has to go on an errand to the mortuary at Scotland Yard and invites her to join him. Bernice didn’t think Mycroft would normally be involved in criminal investigations, but he tells her Dr Watson exaggerated the differences between him and Sherlock for dramatic contrast.

As they stroll towards Scotland Yard, Mycroft explains that he’s noticed a remarkable number of occurrences of the number seven in recent crimes. There doesn’t seem to be any connection between them apart from the number, but he suspects someone is deliberately committing crimes with a recurring motif. Among the instances are the death of seven swans in the Serpentine on the 7th of the month and the theft of seven silver spoons from the seventh Earl of Barchester. The crimes are petty and abstract, and although unpleasant they’re hardly the greatest crimes committed in London. Bernice suggests the pattern might exist for the sole purpose of drawing Mycroft’s attention to it, but he doesn’t think his public profile is sufficient for someone to engage him in this matter. However, this morning he received a visiting card that contained no details or addresses, just the word seven written in various different languages. He’s worried this may be the perpetrator’s way of announcing that he’s moving on to more serious criminal endeavours. He went to Whitehall to study recent crime reports and what he learnt there has led them to the mortuary at Scotland Yard. A constable shows Mycroft and Bernice a body and Bernice instantly recognises him as the keeper she met at Regents Park Zoo when she first arrived. A crushed watch found at the scene shows the murder was committed at seven minutes past seven in the evening.

Over the next month and a half, Bernice and Mycroft worked together on a number of different cases and they develop into quite a good team. They’d almost forgotten about the ‘seven killer’ until they received the message that led took them on a trip to Richmond High Road via the London Underground. With two murders under his belt, it seems likely the killer will strike another five times, so Mycroft devotes all his time and energy into trying to work out who will be the next victim. Bernice is still missing her son and is starting to worry about him, so she determines to get her hands on some means of time travel so she can rejoin him. If all else fails, she’ll write a letter to him and leave it with Mycroft’s lawyers to be collected in the future. In the meantime, she and Mycroft are booked on a train to Tatchester…

Elsewhere, a police constable catches the strange man from Regents Park Zoo defacing some public property. When the officer tries to stop him, the man accuses him of being a pompous peasant interested only in enforcing the status quo. The man pulls out a pistol and proceeds to shoot the constable seven times…

At the Langham Hotel, Septimus informs Lord Straxus that his Time Ring began activating while he was typing up the inventory notes. Straxus examines it and realises the Ring has detected the presence of another time traveller. It had used its emergency setting, which is available only to members of the consular rank such as he, to override the other Ring and draw its operator to this time and place. With the consular lock in place, the owner will now be unable to leave and all Straxus has to do is track down the time traveller and force them to hand over their Ring. Straxus reveals that he’d previously sent out a distress call which suggests the traveller is working for his own people, but whoever they are, Straxus is bound to outrank them. He tells Septimus to fetch his top hat and gloves while he hails a hansom cab.

Hours later, Septimus is getting tired of riding around London in search of the other Time Ring. Straxus mocks him but says they’re not going around randomly. His Ring is ascertaining the position of the other Ring and it’s talking to him and telling him where to look. Certain that it’s close by, Straxus instructs his driver to turn into Pall Mall, then he brings it to a halt not far from the Diogenes Club. The watch people coming and going and then Straxus identifies one of them as Mycroft Holmes, one of the Club’s founders. His Ring tells him the woman standing next to Mycroft has the other Time Ring on her person. He doesn’t recognise her, but Septimus thinks she looks rather charming in a bedraggled sort of way.

Mycroft and Bernice return to their rooms and order tea and food from Mrs Gross to celebrate their victory in solving their most recent case. Mycroft asks Bernice if she noticed they were being followed from the moment they left the Club. They discreetly look out of the window and see two men standing by a nearby cab, paying far too much attention to the house. Bernice is amazed when she recognises the taller of the men, but she’s sure it can’t be who she thinks it is. Mycroft identifies him as Septimus, an odd man who, according to the accounts of Dr Watson, is noted for never blinking. He’s the assistant to Lord Straxus, a dealer in antiques and rare art and something of a minor hero for travelling across the globe finding tombs and blind pyramids to loot and plunder. He notes that the two men are rather animated and he wonders what it is that’s causing them so much interest.

Lord Straxus says he’s certain the other Ring is now inside Mycroft’s house. This bothers him as he knows for certain that Mycroft isn’t working for his people, which means he should have no authorised contact with a temporally active person. He suspects the woman with the Ring might be either a factional, a transuranic or an unauthorised temporal agent, but whatever she is, she’s unlikely to part with the Ring voluntarily, so they’ll have to steal it. Straxus suggests they go back to the Langham Hotel and then later, Septimus can use his Time Ring to enter Mycroft’s rooms and take it while they’re asleep.

Mycroft and Bernice watch the two men leave, then Mycroft explains that they sell their plundered items at private auctions across the country, including monthly sales at the Langham Hotel. The last of their sales here in London was their sixth. Mycroft has a file on Straxus as he’s something of an enigma with possible criminal connections. He’s recently been keeping an eye on his activities on behalf of Sherlock and in fact Sherlock nearly arrested him once before during a case Dr Watson referred to as the ‘Cautionary Disappearance of Ludwig Cooray‘. Cooray was the nephew of a minor German aristocrat who went missing in Ceylon at the same time that Straxus was serving there. Nothing was ever proven and Straxus had a cast-iron alibi as people can’t be in two places at the same time.

Septimus returns to Straxus just before midnight. The occupants of Mycroft’s apartments must be asleep by now, so Straxus re-sets his Time Ring so it can make a quick spatial shift and home in on the other Ring. Septimus points out that every time they use the Ring, it’s more likely to fail again, but Straxus is surprised to hear such cowardice from a soldier. Adjusting to life here has been difficult and he thought Septimus would appreciate the introduction of a little danger. He orders him to get on with the job and moments later Septimus disappears from the hotel……and reappears in Mycroft’s rooms. The occupants are indeed asleep, including Bernice who fails to notice the thief as he searches for what he’s come for. It’s not long before Septimus returns to Straxus and announces that he has the second Ring. Straxus examines it and is pleased to see that it’s not damaged. However, when he tests it, it doesn’t seem to work. He decides to dismantle it to see if there’s a more subtle problem, so he orders Septimus to leave and return in the morning.

Bernice bursts into Mycroft’s room and frantically tells him her Time Ring has disappeared. She tells him she was woken up by a noise, which turned out to be the device disappearing. She’s worried the Ring wasn’t as damaged as she originally thought and that it’s now gone and left her behind.

When Straxus discovers there’s no technical problem with the second Ring, Septimus suggests he ask its original owner, but Straxus suspects they may be agents of their opponents and thinks it‘s unlikely they‘d be prepared to say anything useful. He wonders if the Ring could have a genetic lock on it so that it only works for one person or a group of people who share common genetic ancestry. Satisfied he has the answer, he orders Septimus to find the woman and bring her back here.

Bernice begins writing her letter to Peter and finds it’s one of the hardest things she’s ever had to do. She’d been putting it off in the hope that she might get out of her current situation, but now that she’s lost the Ring she knows there’s no chance of getting back to him. There’s a knock at the front door and when she answers it, she’s amazed to find it’s her old friend and travelling companion Chris Cwej. She thought she recognised him last night in the street outside, but it’s only now she’s seen him up close that she’s sure. However, he says he hasn’t come here to rescue her - then he lashes out and knocks her unconscious.

Bernice wakes up and finds herself tied to a chair in Lord Straxus’s suite in the Langham Hotel. When Chris Cwej joins them she realises the truth - Straxus isn’t an earthly lord at all, but one of the temporal variety. She asks Chris to tell Straxus who she is, but he reveals that he’s not who she thinks he is. He says he’s called Septimus, a name he borrowed from one of their customers who told him he reminded her of her son. He’s a cloned soldier, one of an army that Straxus’s people are growing in order to assist them in practical and military matters. They realise Bernice must have been acquainted with the clone’s progenitor, Christopher Rodonanté Cwej. Straxus regards her official status as dubious and says she therefore has no rights at all, so he advises her to answer his questions quickly or he’ll ask Septimus to employ some of his more extreme interrogation techniques.

Septimus calls on Mycroft and invites him to join him on the other side of the street where he can hail a hansom cab. When Mycroft refuses to accompany him, he reveals that he’s come fully armed. He adds that if that isn’t reason enough to obey him, he could, in fact, muster seven reasons…

Bernice is relieved when Straxus produces her Time Ring. He asks her how she acquired it and she tells him it was given to her by a friend. Septimus reveals that he used Straxus’s second Time Ring to steal hers from her bedroom. She knows his people are keen to stamp out unlicensed time travel, but she thinks things are getting a little petty now. Septimus reveals that they need her Time Ring because Straxus’s one is damaged and although it can move limited distances in space it can’t move at all in time. Bernice laughs and confirms that he won’t be able to use her Ring either as it has a genetic lock.

Just then, another version of the clone Septimus (who refers to himself as Brother Seven) arrives, accompanied by Mycroft. Straxus is surprised to discover that his version of Septimus (Brother Six) activated another copy after Straxus let his predecessor (Brother Five) die. These are the last two of the seven clones of a seventh clone. Straxus confirms that the Cwejen he originally brought here died when the Time Ring shorted out on them during a trip to Ceylon. They’d been using it to jump around the planet, pillaging pyramids and sarcophagi where it was impossible to access them by any other means. Brother Five died in agony and the sixth and seventh versions felt his pain, even though they weren’t even awake then. Straxus used the money to fund their lifestyles here while at the same time sending a subtle distress call to those who monitor the timelines. Selling ancient artefacts that weren’t supposed to be available in this time period was meant to be a way of re-shaping human history in a noticeable but non-destructive way. The Cwejen point out that if Straxus had wanted to be rescued earlier, he could easily have killed someone with an impressive destiny ahead of them - for example, the writer Oscar Wilde is currently staying at this very hotel. Straxus insists that he has a responsibility to history, but the Cwejen think his ideas are too rigid. The two brothers decide to take action themselves and they grab Straxus. They know that a knife through the chest or decapitation are both enough to prevent him from using his people’s much vaunted powers of renewal.

The Cwejen stab Straxus and he collapses, but the brothers reveal that he’s not dead yet and they intend to finish him off later as a bit of a treat. They reveal that each of the Cwejen has a figure lurking in their minds who they’ve served since before they came into being. He’s referred to as the pale god, or Mister Seven. Rather than attracting the attention of Straxus’s masters, they’ve decided to create a pattern in space-time for him to see. Mycroft argues that there’s no pattern for their master to see as there’s no logic or sequence to it, but they tell him it’s one that petty human minds can’t perceive. They claim it was Mycroft’s own intervention and investigation that was indirectly responsible for making their plan a success. It was his cognitive powers that processed the information they were feeding him. By concentrating on the number seven, by trying to draw links between the Cwejen’s actions and by coming into contact with a woman from another time - who they brought here specifically for that purpose - he’s re-shaped his thoughts without even realising it. And that, in turn, has re-shaped reality. Bernice confirms that the theory is known as quantum mnemonics. The Cwejen claim that by working together and mulling over the ingredients of their plan, Bernice and Mycroft have created a scenario where London will burn in an all-consuming fire and when that happens, Mister Seven will descend and pluck them to safety.

All the Cwejen need now is a spark to start the fire…and that spark will come in the shape of a bomb. Bernice is disappointed and says no matter how they try to justify their actions, they’re nothing more than miserable aggrieved gits who want to blow people up to make themselves feel better, but the Cwejen claim that they serve a higher power - the pale, manipulative god known as Time’s Champion! Suddenly the room lights up with a tremendous electric charge and the two Cwejen collapse to the floor. The newly regenerated Lord Straxus stands up and announces that his people would never have allowed their servants to run riot like this. The Cwejen may be biological, but they’re still machines and they have built-in code words that deactivate them. Mycroft is confused about how Straxus changed his entire body, but he points out that it’d be a better idea if they started looking for the bomb. He suggests they start with the auction room as Septimus spent a lot of time there. Bernice tells Straxus to evacuate the hotel, then she demands that he hands over her Time Ring.

Bernice and Mycroft find the auction room is packed full of boxes. Trying to think like a maniac, she wonders where Septimus would have hidden the bomb - but Mycroft reminds her he was a maniac fixated with the number seven. They find the box containing Lot 77 and they break it open to reveal a ticking bomb with a clock indicating they have less than two minutes remaining. Mycroft begins a countdown, but Bernice resorts to smashing the Time Ring against it. The Ring starts powering up, so Bernice picks up the bomb and activates it. She disappears and reappears moments later outside the building. She knows she’s not far enough to survive the explosion, but at least London will be saved. She hurls it as far as she can into the river and then it explodes…

Bernice wakes up and finds herself facing the earlier version of Lord Straxus. She asks him what happened to his new face, but he refuses to answer. She realises they’re both in the Vortex, protected from the swirling, corrosive particles of time by a bubble. Straxus explains that he saved her life by pulling her out of the time stream at the moment the bomb detonated. He reveals that someone did eventually spot the temporal disturbances the Cwejen had caused - and that person was himself, Lord Straxus from an earlier point in his life. He admits that he was rather taken aback when he investigated and found he was involved himself, so he popped back to 1893 to save her as her death at this time would have caused more issues. He also explains that her Time Ring automatically reactivated itself the moment Mycroft handed it to her. The future version of Straxus is now locked up safely and the earlier version intends to ask himself some pretty searching questions later.

Bernice asks what happened to the two Septimuses and he says they’re both awaiting dissection as he needs to make sure the genetic problem that caused their malfunction is eliminated, preferably before it occurs. He believes Septimus was insane, but Bernice says he seemed very cogent to her. She remembers he referred to their ‘god’ as Mister Seven, a shared god amongst the Cwejen, but Straxus says it’s not uncommon for lunatics to seek affirmation for their actions from an imagined higher power. Although death cults often genuinely believe in their gods, that doesn’t mean they’re actually real. His own people tolerate the beliefs of inferior races, but he thinks they shouldn’t if it means those races will react in the way the Cwejen have. Bernice points out that his people may have been partly responsible for the way the Cwejen turned out, especially after Straxus let one of them die. Straxus dismisses the dead brother as nothing more than a copy of a copy.

He hands Bernice back a brand new Time Ring as a parting gift and tells her it shouldn’t give her any problems. He promises she can keep it once she’s returned her to her own time and place. Before Straxus goes, Bernice tells him that one of “his lot” is taking extreme actions and causing problems for the people in the sector of space where she used to live. She asks whether his people plan to do anything about it, but Straxus says he can’t comment and if something needs to be done, it will be done. He suggests she use her Ring to make a few house calls before she returns home and tells her the room at the Langham Hotel formerly occupied by his future self has considerable amounts of contemporary currency in it. The room number is 77. He says goodbye to her and then disappears.