Dorothy and
Tom are on a date to
The Proms. However, the performance of works by
Saint Hildegard of Bingen is interrupted when a mysterious monk tumbles to his death from the gallery.
At the office the next day, Dorothy and Tom are introduced to the new interns, Katya and Balvinder. Dorothy reveals that she has seen a post on the ePi forum to the effect that 'the monks were coming to claim what was rightfully theirs.' The user who posted this was called SaintHildegard, who has since deactivated their account. Dorothy senses something in the air, but can't yet work out quite what, but wonders if it has something to do with the Vavasor papers, which apparently Isaac Vavasor and Kevin Wilbraham have both been spotted chasing after in various parts of the world.
Dorothy suggests that the only person who can help them figure out what's going on is Margot Evercreech, the only person ever to have interviewed Isaac. So Dorothy and Tom go to visit her, where they are greeted by a shotgun-waving Margot and her alpacas, Dolores and Steven. They also find Benjamin Unsworth, who is now working for Margot as her archivist, having been fired by Helen Matheson. It turns out that Isaac was something of an expert on Hildegard of Bingen (and in fact wrote the programme notes for the prom concert that Dorothy and Tom had attended, under the assumed name Ivy Griffin) and that there was also something about monks in an archive of his that Margot previously acquired. However, this archive has gone missing, on a laptop that Margot was also messing around with cryptocurrencies on, including Tulpencoins. Dorothy puts two and two together and deduces that Margot's laptop has been stolen and taken to Channellia, where it sank along with the rest of the rig. She persuades Tom that he should retrieve it.
Tom goes to Burnham-on-Sea, where he encounters the diver Sven who will take him out to the submerged rig, five miles out, the next morning. In the Jolly Sailor that night, he also comes across the mysterious Jasper Bancroft, who gives him his card. The next morning, Sven takes Tom out to the submerged Channellia and he dives down to fetch Margot's laptop. On his way back to the surface, he is attacked by someone with a harpoon, who he fends off by hurling his weight belt at them. When he breaks surface, he finds that Sven has vanished. Unexpectedly, Bancroft shows up to rescue him, but he in turn is shot by the man with the harpoon. Tom manages to escape back to Burnham and finds that Sven has vanished, apparently gone fishing.
Tom goes back to London with Margot's laptop and he and Dorothy persuade her business partner Ali to retrieve the archive from it. This reveals that in the course of Isaac's research into Hildegard of Bingen, a person known only as S had brokered a meeting with a mysterious monk, who in turn had expressed a desire to meet Archie and Pye, as his order was interested in making use of their mathematical expertise, specifically in the area of fractals. However, the only thing that ultimately came out of this was work that would turn out to be useful in their subsequent relationship with the Belarusian mafia. S, meanwhile had disappeared off the face of the earth.
Having reached a dead end, Tom decides to go back to Burnham-on-Sea to find out why he was abandoned by Sven. On a tip-off, he heads over to the lighthouse where a trail of blood leads to Sven's body, wrapped in a monk's habit, hidden in the rough on Burnham golf course. Having reached yet another dead end, Tom remembers that he has Bancroft's business card, so he rings the number on it. Helen Matheson answers, but Tom fails to get any useful information out of her. Meanwhile, a helicopter lands and a group of monks leap out of it and retrieve Sven's body. Tom notices a mysterious symbol on the monks' robes.
Back in London, Tom shows a sketch of the symbol to Dorothy, but it means nothing to her. Instead, she and Tom go off to see Margot again. However, when they get there, Margot's house has been completely emptied, Alpacas and all. Their taxi driver mentions that she was visited by some monks recently, possibly from Greece, with a name that sounds like the Order of the Roman something. When they get back to the office, Dorothy decides they need to seek advice from an expert on monks, so she sends Tom to the Roman Catholic Church of St Wilgefortis the Divine where he meets Father Donal. When he starts to describe the monks, however, Father Donal becomes terrified and orders Tom to leave, go home and forget everything about them.
Later that night, Dorothy and Tom try to break into the Presbytery to steal Father Donal's book of monks, but instead they find Father Donal dead, having eaten one of the pages of the book before committing suicide. The next evening, they go round to Patrice's flat again, where it turns out that she is cooking Romanesco cauliflower for their evening meal, and Tom realises that this is the design on the monks' robes. Patrice explains that this is an example of a fractal pattern, and indeed it seems that, on searching for information on the Order of the Romanesco, they are also known as the Fractal Monks. Dorothy asks for information on the Vavasorology.com forum, but the thread gets immediately deleted and she is barred. eventually, they manage to find a notice about a forthcoming funeral of Brother Anselm, a member of the order, at North Greaseby Priory.
Tom goes to North Greaseby and sneaks his way into the Priory in time for the funeral, disguising himself in monks' robes. It turns out that the person being buried is in fact Sven the diver. Tom also catches a glimpse of someone unexpected, also disguised as a monk - Helen Matheson. However, any further investigation is cut short when Tom is overcome by chloroform and kidnapped by Margot and Benjamin, who are also there, undertaking their own investigation. Margot is suspicious of Tom and thinks he is involved with the monks somehow.
Margot, Benjamin and the two alpacas are now hiding out on a farm. Tom escapes by getting Dolores to nibble through the rope tying his hands together, and he escapes in Margot's van, taking the two alpacas with him. Tom leaves the alpacas in the care of his father's friend Mad Dog McFish and abandons the van, after removing from it a card key for the Norwich branch of STUFF YOUR STUFF, a self-storage facility. They locate Margot's lock-up and extract the most interesting-looking boxes of her archives. However, at this point, they are trapped by a pair of monks. They manage to escape, noting on exiting the facility that the security guard at the entrance has had his throat slit.
On the way back to London, Tom texts Ali to warn her that she and Patrice may be in danger, and Ali responds by saying that Patrice's flat has already been ransacked. They go straight there and find that the disc drive from Margot's laptop hasn't been touched, although Patrice's papers are in a completely mess. Back at their flat, Dorothy does some research on Patrice and finds out that her PhD was in the field of fractals. She also finds a cassette tape among Margot's archives from STUFF YOUR STUFF, but the only person they know who has a cassette player is Tom's dad.
The cassette turns out to be a recording of a rambling and possibly drunk interview between Galton Felmersham, the first biographer of Archie and Pye, and Archie and Pye themselves, in which they describe their meeting with the Head of the Order of the Romanesco at their mountain-top monastery. However, before they can find anything useful from the tape, it gets eaten by the cassette player and ends up breaking it.
Having reached another dead end, Dorothy and Tom discuss what they know so far. Tom admits that he told Bancroft about where he was staying in Burnham-on-Sea, and he also reveals that he left his notebook behind. Dorothy deduces that Bancroft must have stolen this on behalf of the monks and that they subsequently killed him to keep him quiet. This was how they found their way to both Margot and Patrice. She adds that the monks probably killed Sven to keep him quiet as well. Dorothy decides that she'd like to take a look at The Priory herself, so they both go to visit it. However, it turns out to be abandoned and booby-trapped. As soon as Dorothy opens the door, the entire place blows up.
Back at the office, Ali has been behaving strangely and finally owns up that the only copy left of Patti's PhD thesis was stolen in the break-in and that she is distraught about this, but won't say why. She has also thrown Ali out for asking too many questions. Dorothy speculates that the monks came for Margot's laptop but stumbled on Patrice's thesis and took that instead. Apparently he research was in the field of fractals, and the thesis itself was classified for some reason. They resolve to retrieve it before any damage is done.
Based on the fragments of conversation that they'd picked up from the interview tape, Dorothy deduces that the monks' monastery is somewhere in the area of Meteora in Greece. Dorothy and Tom fly out there, taking Tom's and Margot's robes with them as disguises. They quickly establish that the monks must be based at The monastery of St Benoit at the top of one of the mountains in the area. They ascend to the top via wicker basket and sneak into the Great Hall, where Matins is about to commence and they watch the monks perform their extraordinary Fractal Dance. In the middle of it all, the Abbott produces an impressive leather-bound book, which they recognise as Patrice's PhD thesis. After the ceremony, they follow the Abbott and his crew to the library, but they are unable to get in and they are hustled away by a couple of monks acting as security.
However, it turns that the supposed security detail in fact consists of Margot and Benjamin, who are also here trying to solve the mystery of the monks. Once their respective identities have been revealed, Margot and Benjamin leave them to it, and they decide to create a diversion by releasing the pigs from the monastery's pens. In the ensuing chaos, Dorothy and Tom manage to sneak into the library and find their way down into the lower depths where they find someone reading the thesis on his own in the darkness: Isaac Vavasor. Isaac relates the history of the Order up to the point where Patrice's PD thesis was commissioned, with Archie and Pye as her supervisors. Her thesis was supposed to find God in fractals, but she ended up finding a truly terrible pattern that destroyed everyone who came near it. This led to a crisis in the Order, whereby the old Abbott ordered her research to be destroyed, following which he was found dead. A new Abbott reversed the policy and sent out the order to find the one remaining copy.
Isaac has been sheltered by friends of the old Abbott's side of the schism, but now it is time for him to escape, with Dorothy and Tom, who take charge of the thesis. Unfortunately, they are discovered and the library is - in the grand tradition of libraries in fiction - set alight. The three of them succeed in escaping the burning building and emerge into the increasing chaos outside. They take a tortuous path towards the exit, in the course of which Isaac grabs the thesis himself and runs off. They eventually find Isaac in the bell tower, mortally wounded and without the book, which is now in the hands of his murderer, who is standing over him. Margot and Benjamin also show up at the same time and Margot and Isaac effect a reconciliation before he dies. In a fit of rage, Margot overpowers the other monk and grabs the book. The four of them make their escape and find their way to the wicker basket lift, only to run into Helen Matheson and her cronies.
Matheson forces them to hand over the thesis and goes off to find Isaac. Margot and Benjamin escape in the basket lift and Dorothy and Tom chase after Matheson's bunch. They find one of her men corned by a couple of angry pigs and retrieve the book from him and head back to the lift. Halfway down, they are menaced by a helicopter, which they stave off by throwing the thesis at it. The thesis gets shredded in the blades and the helicopter crashes to its destruction.
Back at Patrice's, they own up to the loss of her thesis, but Patrice is unexpectedly relieved, now that the final copy, which she had kept for herself against all the rules, has been destroyed. Tying up loose ends, Dorothy wonders if it wasn't Bancroft who stole Tom's notebook after all, but one of the monks, alerted to Tom's presence by another shadowy figure from Tom's past, such as
The Hon Sholto Chelford-Bickerton, whose name just happens to start with S. However, this speculation is brought to a halt by the discovery of a note from Katya, indicating that her uncle
Arkady wants her to call him. What on earth can he want?
