After returning from E-Space and being offered a seat on the High Council, Romanadvoratrelundar has now been elected the new President of the Time Lords. While tidying up some of the loose ends left by her predecessor, she learns from Castellan Spandrell that a Fortean flicker has been detected, emanating from a distant planet. They investigate its source and finds a band of humans trapped in a null-time zone with angry Chelonian warriors. Romana and Spandrell rescue the stranded humans, return them home to 20th-century Earth, and then return to Gallifrey -- where Spandrell investigates further and discovers that the Fortean flicker was used as a distraction. Someone has stolen the ancient Loom of Rassilon’s Mouse.

Benny Summerfield and Jason Kane are getting married, and the Doctor has taken them to early 21st-century Cheldon Bonniface. Here, they will be wed by Ernest Trelaw’s niece, Annie, in St Christopher’s Church, as witnessed by the spirit Saul and the new verger, James. Several of Benny’s friends will be attending the ceremony, and in order to avoid attracting unwanted attention from the townsfolk, the Doctor supplies the aliens -- such as the Pakhar newscaster Keri and her cameraman, Kitai -- with holographic disguises which make them appear human. Only a few villagers know the truth, but the odd behaviour of the new arrivals is starting to cause some mistrust and suspicion amongst the locals. Benny and Jason have been arguing and fighting almost constantly, as Benny isn’t sure whether Jason really loves her or has just fixated on her because she’s the first human woman he’s seen after spending fifteen years alone in the Dagellan Cluster. When Dorothée McShane (formerly known as Ace) arrives for the wedding, riding a motorcycle rigged to travel through Time, Jason begins to flirt with her -- much to Benny’s irritation.

The Doctor and Dorothée set off together to collect the musical guests for the wedding. The Isley Brothers are surprised when the TARDIS materialises in their living room, but are delighted to learn that the time-travelling Doctor is a fan and enthusiastically agree to travel into the future to play at the wedding. The Doctor then travels to 1997 to pick up Danny Pain, choosing not to tell him that by the time of the wedding he has died in a car accident. Two gay Silurian lounge singers, Jacquilian and Sanki, visit from the 30th century, while the men known to the public as Sherlock Holmes and Doctor John Watson arrive from the 19th. Meanwhile, Keri discovers that Kitai has rigged her holographic disguise in the form of a 26th-century porn star, and when she confronts him, he changes it... so that she resembles a member of the British royal family. She also discovers that she and Kitai are allergic to the pollen in the air, and that whenever she sneezes, it triggers a momentary psychotic hallucinatory state.

Roz, feeling at a loose end amongst the happiness, takes to wandering in the fields outside town, and on one such walk she finds a scrap of paper which seems to indicate that someone has been smuggling the illegal chemical Bloom. However, she is unable to interest Chris, who is far more interested in his fling with Ishtar Hutchings. Peter and Emily are furious when they learn, but can do little about it. Ishtar feels strangely at home inside the TARDIS, and is constantly giving Chris presents which appear to have come from different time zones. While out at a pub in the nearby village of Tasham, Chris and Ishtar hear a woman talking about her fling with a man who claimed to be from outer space, and conclude that Jason is already cheating on Benny. When Ishtar tells her, Benny furiously convinces Keri to change her holographic disguise to resemble Ishtar and go flirt with Jason to see what happens. She then goes on a pub crawl with Dorothée, but upon entering the pub where “Ishtar” and Jason are kissing, she loses her temper and attacks Keri, accidentally switching off her hologram and revealing her true hamster-like form. Chris angrily confronts Jason, who also switches off his holographic disguise to reveal that he’s really Kitai, who disguised himself as Jason as a prank. Fortunately, Keri and Kitai escape from the pub before the shocked townspeople can react.

Rumours of the odd incident spread quickly, but fortunately Brigadier Lethbridge-Stewart, Doris, Benton and Mike Yates arrive in town for the wedding, and the Brigadier contacts his associates at UNIT to ensure that a security blackout is established for the duration of the festivities. Less fortunately, paranormal investigators Hamlet Macbeth and Ruby Duvall also arrive in town, and the Doctor finds his hands full trying to avoid them -- especially Macbeth. The Brigadier is delighted when Kadiatu and aM!xitsu arrive, proving that his legacy will continue into the future; however, he’s less pleased when he finds he can’t remember Bernice. The Doctor finally admits to tampering with the Brigadier’s memory in order to preserve his sanity after the Vardan invasion, and puts things right again. The Brigadier then informs the Doctor that he has only weeks, possibly days, to live; he has accepted his fate, and asks only that the Doctor see to it that Doris, Kate and Gordy live long and healthy lives.

Sherlock Holmes, feeling at a loss in the 21st century, finds a kindred spirit in Roz and agrees to help her investigate the smuggling operation. In order to do so properly, he plunges into a study of the customs and technology of this unfamiliar century in order to provide himself with background for his deductions. Meanwhile, Dorothée decides to find out whether Jason is really serious about marrying Benny and tries to seduce him. He resists her advances and leaves, but then returns moments later and makes love to her, apparently having changed his mind. She must now decide how to tell Benny about it, but is unaware that Emily has overheard it all and is using it as fodder for her next novel.

That night at the pub, James the verger enters bearing decorative wreaths -- and the pollen from the wreaths sends Keri and Kitai into psychotic fugues. As the Doctor and his friends try to smooth over their strange behaviour, lightning strikes an alien device on the pub roof, deactivating the aliens’ and Silurians’ holographic disguises. Macbeth then sees and recognises the Doctor, and the frightened townsfolk form a mob and chase the aliens out of the pub. Benny, Jason and their friends from UNIT manage to redirect the mob and hold them off until the aliens can reach the church. There, Annie grants the aliens sanctuary, and Saul begins to broadcast a calming empathic effect. Once the townfolk enter the church and see that the aliens are just people like themselves, they calm down. Even Macbeth greets them with awe rather than fear and hatred, and after this night, the townsfolk respond with fascination and friendliness to the aliens in their midst.

The Doctor sets up rehearsal spaces in the TARDIS for the Isley Brothers, Plasticine, and Sanki and Jacquilian, and plans a cricket match to cement good relations between the townsfolk and the alien newcomers. More visitors arrive, including Irving Braxiatel, the crew of the Schirron Dream and Captain Lisa Deranne of the Tiger Moth; they too join in the cricket match. Macbeth plays on the Doctor’s team, and the aliens, cheered on by the town’s children, win the game. Savaar and an escort of Ice Warriors then arrive for the wedding just as UNIT troops arrive in the village in response to the Brigadier’s request for a media blackout, but Benny and the Brigadier are able to prevent any immediate conflict. Unfortunately, that night the Ice Warriors and UNIT troops get involved in a pub brawl just as the Bishop of the diocese arrives to investigate the rumours of odd events in the village. While Annie tries to explain herself to him, the Doctor notices that O’Reilly Isley has found a song which he hasn’t written yet, “Summer Breeze”, on the jukebox. The Doctor stops him from listening to it, warning him that if he simply copies it down instead of originating it himself, that will mean that it was in fact written by Time herself -- and such things can be terribly dangerous. Despite the Doctor’s warning, however, O’Reilly looks it up elsewhere, feeling somehow that it’s important.

Maire and her fellow Travellers arrive and convince Benny to undergo a handfasting, a pagan bonding ceremony which uses nanotech to bond them in cyberspace. Emily, Savaar, the Doctor and Dorothée also participate in the bonding ceremony, where Jason and Benny commune with old lovers and lay old ghosts to rest. Benny comes to terms with her murder of the Nazi private Gerhard, who did after all die for his country, and Jason rejects Dorothée when she makes advances to him. Having assisted in the ceremony, Emily finally comes to terms with her daughter’s relationship with Chris. Meanwhile, the villagers begin to behave strangely, and Kadiatu sees them all enter trances and head for the church; at the same time, Keri sees James the verger arguing with someone who apparently shoots him, but she sneezes at the same time that James’ body vanishes, and remains unsure whether she’s actually seen someone murder James or not. The villagers return to normal, unaware that anything unusual has happened.

As the handfasting ends, Muldwych the magician arrives on the back of a unicorn, having escaped from Antýkhon by travelling into the cyberspace plane of reality along a beam of chronons. At the same time, the Doctor’s old TARDIS, thought destroyed on a parallel Earth, materialises on the village green, piloted by the descendents of the Charrl whom Muldwych had trapped inside. Muldwych explains that it was saved from the Time Ram by travelling on the wave patterns of a Fortean flicker, which also explains the wild coincidences which have been happening in Cheldon Bonniface recently. The Doctor invites the Charrl to the wedding, and continues to pick up guests, including William Blake, Vivant Denon, Forgwyn and Alexander Shuttleworth.

Holmes finishes his research, and with Roz’s help, narrows down the list of possible suspects. On the grounds of Steel Farms, they find a barn containing numerous severed body parts. Although Chris remains entirely uninterested, the Brigadier accompanies them when they confront the farm’s owner, Alec Steel, or Lord Tasham. Tasham has already demonstrated some familiarity with the Doctor, and when questioned he admits that he used to be an unscrupulous man concerned only with himself -- until he encountered the young couple Vincent and Justine Wheaton and was shown the error of his ways. He has been purchasing the Bloom in order to keep it out of the hands of those who would actually use it until he can find a way to dispose of it. At first, Roz and Holmes assume that the limbs in the barn are the result of a shipping accident, but Tasham has no idea what they’re talking about -- and when they investigate, they find that the barn has disappeared, as have Tasham’s carefully hoarded supplies of Bloom.

The night before the wedding, the visitors throw hen and stag parties for Benny and Jason. The men get Jason drunk and leave him tied up in his underwear in the Charrl’s TARDIS. As they return, the women ambush them outside the cemetery, using aM!xitsu’s technology to disguise themselves as Phractons. Something very odd then happens, but nobody can remember what it is when they wake up the next morning; considering their state the night before, however, nobody finds this unusual. As the hour of the wedding approaches, Kadiatu discovers that aM!xitsu has gone off-line, apparently having chosen an inopportune moment for a full memory core dump. Only the Doctor remembers what happened, and he’s investigating it in four different places simultaneously.

Despite Benny’s growing jitters and her uncertainty about Jason’s faithfulness, she nevertheless shows up at the church for the wedding. The ceremony begins with a sermon from Annie about the importance of peace, but is then interrupted by a boxer-clad Jason, who has just escaped from the Charrl’s TARDIS -- and who is surprised to see himself already standing at the altar with Benny. At that moment a crowd of clones stumbles up out of the crypt, and in the confusion the Bishop reveals himself to be the Master in disguise and takes Benny hostage. The Master reveals that he caused a Fortean flicker as a distraction while he stole the Loom of Rassilon’s Mouse from Gallifrey, intending to weave a strong, healthy body for himself. To that end, he stole Tasham’s Bloom, and has been conducting cloning experiments on the head of the late Anthony Rupert Hemmings. However, the coincidences generated by the Fortean flicker have backfired upon him, since the Doctor coincidentally chose the same town for Benny’s wedding.

The Master has been trying to disrupt the wedding so he can continue his work in peace, and to that end he generated a clone of Jason who would sleep with Ace, and hypnotically conditioned Chris to take no interest in the odd events. James the verger was in fact an android who focussed the Master’s post-hypnotic commands; however, James was constructed using Tzun technology, which reacted poorly to the technology the Doctor had been using to generate the aliens’ holographic disguises. As a result James’ commands were causing the villagers to behave strangely, and the Master was forced to dispose of him. By now, however, his experiments have now been disrupted for too long, and the Bloom in the cemetery is erupting. Last night an eruption knocked out the hen and stag party guests, and generated clones of them; the Master erased their memories and forced aM!xitsu to shut down. But now the Bloom is erupting again, and before the Master can stop it, a monstrous protoplasmic blob generated from Hemmings’ remains bursts up through the floor and attacks the wedding guests. The Brigadier is consumed by the blob while saving the Silurian Jacquilian’s life; the Doctor thought he’d known how the Brigadier was fated to die, but thanks to the Fortean flicker, all bets are now off. He thus urges Ishtar to tap into her repressed memories of being the Timewyrm, and she is thus able to release a blast of temporal energy which destroys the creature. As a side-effect, the Brigadier is not only saved, but restored to youth. The Master then attempts to escape, but Benny and Jason overpower and disarm him, and he is placed under arrest and marched away by the UNIT troops. Without further ado, Jason and Benny become man and wife.

Later, at the reception, the Isley Brothers perform “Summer Breeze”, but Muldwych assures the agitated Doctor that it will be all right this time; they have been granted a special grace for this wedding. Even Ace’s mother shows up for the festivities, along with her boyfriend, Robin Yeadon. The Doctor decides to slip out quietly and leave his companions behind; after seeing the Nazis torture Benny, he no longer wishes to risk harm to his friends. However, Benny stops him from going; nobody deserves to be alone, not even him.

Further guests attend the reception, including saRa!qava, who has now become male, and who informs Benny that her daughter Dep has had a daughter of her own, iKrissi. Other guests include: Liso; James Rafferty; the grey man; Anne Doras’ daughter Bernice; Damakort, Alpha Centauri and Professor Rhukk; the former Master of the Land of Fiction; Petion; Kim Talevara; Manda Sutton; Benjamin and Cristian Alvarez; Francis and Elaine from Arcadia; Mikhail Popov; Gilgamesh; Richard and Charlotte Aickland; Creed McIlveen; Provost-Major Beltempest and Doc Dantalion; Herne and Old Davy; and Tom Dekker. The cake is designed by Leonardo da Vinci, and Benny has a brush with a strange young Goth girl who seems oddly familiar. In fact, she’s met Benny twice.

Romana and Spandrell collect the Loom and apparently take the Master into custody -- but their captive is revealed to be Kitai in disguise, as the real Master has hypnotised him and escaped once again. Dorothée returns to 19th-century Paris with Jason’s clone, while the Doctor takes the other guests back to their proper times and places. Later, in 1998, Danny Pain narrowly escapes death in a car accident when he pauses at just the right moment to listen to “Summer Breeze” on a nearby radio. Ishtar admits to her parents that she’s always had a special relationship with Time, but that she kept it secret for fear of what they’d say; however, now that they’re all comfortable with it, she informs them that she’s pregnant with Chris’ child and that her daughter Jasmine -- and Jasmine’s boyfriend Ricky -- will have a very positive influence on future history. The Doctor switches TARDISes with the Charrl, getting back his old one and giving the alternate Universe’s version to Muldwych. He then drops off Jason and Benny on the planet Plautus for their honeymoon, and departs with Roz and Chris, off on new adventures while Benny and Jason celebrate a love for all seasons.