La noche de San Juan (Trilogía de la Noche, 1)

To overcome his personal problems, Inspector Gabriel Somoza moves into his parents' old house on the Alicante coast: a secluded spot filled with happy memories. However, his plans for tranquility are shattered when he discovers that the previous tenant disappeared under mysterious circumstances and realizes that the neighbors know more than they're letting on. What begins as curiosity soon turns into an obsession. Driven by an instinct he thought he'd buried, Gabriel begins to piece together a disturbing puzzle that only someone like him can solve.