The Missing Ones, Edwin Hill’s second Hester Thursby novel, is a complex mystery with well-defined characters, a detailed plot, and suspense that tightens like a vise. In Somerville, Massachusetts, Hester is caring for Kate, the abandoned four-year-old daughter of her best friend, Daphne. Hester’s having her own problems, too, since she was nearly killed by a man who hired her to find a woman who didn’t want to be found. Hester hasn’t been to her job as a research librarian in a month and she’s afraid of leaving Kate at school.

On Maine’s Finisterre Island, a tourist stop during the summer months, a boy goes missing on the Fourth of July. He’s found a few hours later sleeping in a boat, but there are whispers about what really happened. Annie, a troubled woman living in an abandoned Victorian house where junkies and vagrants congregate, finds herself at the center of a search for another missing four-year-old boy. Annie thinks the two disappearances are connected, and when she begins to suspect a corrupt police officer, she becomes paranoid and scared. With a major plot twist, Hester is drawn to the island also, where she is forced to face both her fears and her past.

The Missing Ones’ sprawling, but effective, plot is built around its characters: a fisherman with an unscrupulous reputation, a local cop with eyes for a married woman, a state police detective with a mean streak. But it’s Annie who steals the show. Her mysterious backstory and uncertain motives add texture and grit to what could have been a too-smooth and generic crime thriller. Hester is more of an observer than actual participant until the final few chapters, but Hill’s expert rendering of her emotional state makes her relevant and interesting. The climactic scenes have their share of surprises, but for The Missing Ones, the emotional impact of the characters is as important as the mystery.