The Aurelia has just left Tokyo on its way to Thailand when Jermaine falls ill with a mysterious illness. The ship’s physician, Dr. Hanso Kim, confirms that Jermaine has the virus that has struck many of the passengers and crew. The best that can be done for him and the rest of the suffering is to move them into sick bay, which is already overflowing.

Through a Patricia-planned sting operation, she’s come into possession of a wallet belonging to Doctor Benyani Mendoza. Jermaine taught Madam how to access the central registry, which is how Patricia finds his cabin. When she tries to return it, however, a stranger answers her knock and attempts to take the wallet himself, as well as block her from glimpsing the sophisticated lab equipment inside. However, he doesn’t know the wily Mrs. Fisher, who insists on meeting the wallet’s owner before handing it over; when he comes to the door, the good doctor is clearly frightened of the thugs in his room and can barely communicate with Patricia beyond a series of anxious blinks, which is when she knows something bad is afoot.

Captain Huntley sends Commander Shriver to investigate the matter; all she finds is a group of Asian men and women drunkenly playing cards. The Commander assumes Patricia is seeking attention and warns her against further intrusion, as she takes a dim view of her past sleuthing. When Captain Huntley — Alastair to Patricia — falls victim to the virus, Shriver takes command of the ship in such an authoritarian manner that Patricia realizes she and Dr. Kim — who also understands the danger —are on their own, except for several crew members, including Barbie, Baker, Bhukari, and Pippin, who trust Patricia’s skills and reject Shriver’s oppressive leadership.

As more passengers fall ill, the medical crew stretches beyond its limit, and Dr. Mendoza clearly yoked by his colleague, Dr. Chouxiang, Patricia and her team add two elderly pickpockets and their young n’er-do-well companion to their roster in order to sort out everything. The ship anchors just off the coast of West Houptiou, ostensibly for help from a disease control organization, but when US Navy ships start cruising by, Patricia and her crew know something serious is afoot.

Steve Higgs has penned yet another terrific mystery for fans of the intrepid Mrs. Fisher, who once again proves she can’t be deterred. This fifth novel is a joy to read, and reaching the end only makes waiting for the next adventure interminable.