A melodramatic plot full of improbable developments mars Preston and Child’s 16th thriller featuring FBI agent Aloysius Pendergast (after 2015’s Crimson Shore). Pendergast is believed dead after he was seriously wounded and fell into the sea off Exmouth, Mass. Soon after Pendergast’s ward, Constance Greene, returns from Exmouth, she’s abducted from the Manhattan home she shared with the FBI agent. Proctor, Pendergast’s factotum, embarks on a lengthy and convoluted quest to rescue Constance, which takes him to the Kalahari Desert. Proctor’s resolve is strengthened by his belief that Constance’s abductor is Pendergast’s evil brother, Diogenes, who was thought to have died after Constance tossed him into a volcano more than three years earlier. Meanwhile, a sophisticated villain who maintains a secret identity believes that his DNA at a crime scene won’t be matched to a sample in the FBI database because that sample will also be a match for his alias. This entry lacks the originality and chills of the better books in this bestselling series. Agent: Eric Simonoff, WME. (Oct.)