Benny awakens the morning after an overenthusiastic end-of-term pub crawl to find that she's been brought to the estate of the industrialist Krytell, who needs someone with her unique talents to carry out an unusual mission for him. Some time ago, Krytell came into possession of an Olabrian joy-luck crystal; the Olabrians have gained great peace and tranquility from these crystals, and have been known to slaughter the populations of entire planets for looking at said crystals in the wrong way. Before Krytell could arrange the crystal's return, it was stolen by the master thief known as the Cat's Paw, who has since contacted him and arranged to sell it back. The hand-off is to take place on the maiden voyage of the Titanian Queen, a cruise ship taking the most elevated of the upper crust on a tour of the galaxy. Benny agrees to act as Krytell's agent for the trade, and boards the Queen in the guise of a nouvelle riche young widow. She is accompanied by Krugor, a genetically engineered bodyguard grown from the same stock as the ship's stewards, but soon realizes he's really there to keep an eye on her. The ship itself is largely automated, and carries only a token crew to ensure nothing goes wrong with the ARVID, a biocomputer from the Catan Nebula which possesses a childish sense of humour. Shortly after the ship departs from Dellah, however, someone slips into the bridge while nobody's looking and makes a minor alteration to the ARVID's programming. Few notice when its behaviour subsequently begins to change slightly...
Many of the galaxy's most renowned detectives and investigators have boarded the Queen, following the rumours that the Cat's Paw is also aboard. Benny soon befriends Khaarli Czhan of the Dagellan Cluster, and even finds a soft spot for Emil Dupont of Nova Belgique, who has a talent for unnecessarily complicated conspiracy theories which bear absolutely no relation whatsoever to reality. She is much less impressed with the xenophobic and borderline psychotic Sandford Groke of the Catan Nebula, and the less said about her snobby and pretentious fellow passengers the better; however, with Krugor at her side she is unable to do anything about it, even when the overwhelming Dowager Duchess of Gharl snaps at the mousy young Isobel Blaine. Eventually Benny receives a message from the Cat's Paw directing her to the theatre, where she must suffer through a production of Titus Andronicus with a tacked-on happy ending before she can go backstage. There, she finds the Olabrian joy-luck crystal hidden amongst the props, but is hit over the back of the head before she can take it. When she awakens, she finds Krugor's dead body lying next to her, holding the shattered remains of the crystal.
Benny avoids dealing with the suddenly very complicated situation by locking herself in the cabin and trying to piece the joy-luck crystal back together. Oddly, nobody reports finding the body, and she eventually falls asleep; she assumes this was due to exhaustion, unaware for the moment that this was not in fact the case. Driven out of her cabin by hunger, she stops off first to deposit some of her valuables in the purser's safe, which has been placed under guard following a failed break-in attempt; the safe contains all of the passengers' real jewellery, while they wear paste imitations for show. Benny goes on to attend one of the ship's extravagant dinners, but every single one of the courses contains meat or animal by-products of some kind, and as a committed vegetarian she is unable to eat a bite.
The lights in the dining room unexpectedly go off, and during the momentary darkness, a passenger named Sheen slips Benny a note asking to meet with her later. When the lights go back on, the Dowager Duchess of Gharl discovers that her priceless pendant -- which, unlike the other gemstones in the room, was real -- has been stolen. She takes a drink of wine to steady her nerves and promptly explodes, as do several other passengers before they realize that the wine has been spiked with puffer-fish venom. By the time Benny is able to get out of the chaotic dining room, she finds that Sheen too has been killed; someone has sabotaged his commode and sucked him out of the ship into hyperspace. Benny accompanies the crew into the rattier, older service areas of the ship to investigate further, but the crewmember trying to leave the ship discovers the hard way that the oxygen in the spacesuit tanks has been replaced with hallucinogenic gas.
Shortly afterwards, the passenger Nerode dies when the music in the disco is tuned to a wavelength which triggers a fatal epileptic seizure. Over the next few days several passengers are killed in inventively gruesome ways, but despite the horrific nature of the crimes, the remaining passengers seem to treat it all as a game, as if certain that nothing of the sort could ever happen to them. The detectives are unable to identify the killer, and Groke in particular seems close to breaking point. Benny successfully reassembles the joy-luck crystal, only to find that once complete it makes irritatingly ethereal chiming noises while voicing senseless pseudo-platitudes. While working, she has come to certain conclusions about the crimes on the ship; she needs help to confirm them, however, and must reluctantly contact her ex-husband Jason. The ship has just arrived in orbit around the planet Shokesh, and Jason directs her to an area of the planet where stolen goods can easily be fenced. There, she sees a familiar face -- the mousy Isobel Blaine, who admits that she is the Cat's Paw.
Blaine admits to stealing the Duchess' pendant and other precious gems from the passengers, as was her intention when she chose the Queen as the site of the trade-off with Krytell. She broke into the purser's safe early in the journey and switched the real jewellery with the paste imitations; she then faked a second, bungled attempt to rob the safe, thus ensuring that the imitations were placed under heavy guard while the passengers unknowingly left the real jewellery carelessly lying around. She was forced to gas Benny in order to switch about the jewellery in her room, which is why Benny fell asleep earlier despite the stress she was under. She insists, however, that she is not responsible for the murders, and after she explains her true identity to Benny, Benny comes to believe her. Benny and Blaine return to the Queen and break into Krugor's cabin, where they find a list of the murder victims. Benny confirms her impression that the service areas of the ship are older and more worn than the passenger areas, and checks out the escape pods, which have been stripped of all vital equipment. When Blaine reveals that she used a syringe of nano-drones from the Catan Nebula to reprogramme ARVID to ignore her activities aboard ship, Benny puts the last of the pieces together.
As the ship departs from Shokesh, Benny summons the survivors -- who have all remained aboard, certain that nothing bad can happen to them personally -- to reveal the truth. Like Sandford Groke, the Cat's Paw is an artificial assassin from the Catan Nebula, where personalities constructed in computer models are installed in genetically engineered bodies. They were programmed with false personal histories which would make them ideal assassins; Groke, for example, believes himself to be a gentleman adventurer from Victorian London who has been transported through Time by his nemesis, the fiendish Doctor Po. The Cat's Paw was designed as the illegitimate daughter of an evil warlord, who spent her life trying to topple his empire, and at first she believed he had captured her and used dark magicks to cast her through Time as well. Although at first they believed the people they were being told to kill were agents of their enemies, they eventually became aware of the inconsistencies in their backstories and learned the truth.
Whereas Groke retreated into psychotic denial, the Cat's Paw, vowing never to kill again, used her skills to steal from the rich and powerful who had created her as their unwilling agent. Unfortunately, the people she has been trying to punish, including Krytell, have out-thought her yet again. The Titanian Queen is a death ship which was intended to be wrecked for the insurance money, which is why the service areas look so old even though this is supposedly the ship's maiden voyage. Whereas most of the passengers were simply unlucky enough to fall for the publicity, some of them had had contracts taken out on their life for various reasons; these are the ones who have been murdered. Benny now reveals that they were murdered by the ARVID and the genetically manufactured ship's stewards which it controls; the nano-drones which the Cat's Paw used were in fact supplied to her by her former "owners", and in addition to blanking her presence to the ship's sensors they have transformed the ARVID into the fiendish Doctor Po.
ARVID, exposed, prepares to kill the remaining passengers as entertainingly as possible before destroying the ship, but before it can do so the Cat's Paw -- undetected by its sensors -- hooks it up to the joy-luck crystal, and Doctor Po's personality is swept away in a haze of platitudes and ethereal chiming music. Without ARVID to control it, the Queen is left drifting in space, and Benny and Khaarli, the only two qualified passengers, take the single functioning escape pod to seek help. Upon departing from the ship, however, they are attacked by Krugor, who had faked his own death by killing a steward, and remained hidden to ensure that all went according to plan. In the ensuing struggle, Benny accidentally injects him with one of Blaine's backup syringes of Catan nano-drones, and Krugor takes on the personality of Sandford Groke's loyal manservant.
The escape pod's navigational systems have been destroyed, but fortunately a passing ship picks up its distress call and the Queen's passengers are returned to Shokesh. Before leaving, Benny watches as Emil Dupont's attempt to explain that Nerode was really killed by a trio of trained poodles armed with a clockwork-powered sonic gun causes Nerode's already stressed widow to snap; before she realizes what she's saying, she's admitted to murdering him herself. Benny, amused, hitch-hikes back to Dellah, paying her way with the jewellery which Krytell loaned her for the mission. Krytell soon has other things to worry about, however; the Cat's Paw has returned the shattered remains of the joy-luck crystal to his mansion and has informed the Olabrian government exactly where they can be located...
Source: Cameron Dixon