Two years after her spouse’s suspicious death, Lisa Mandel (Patty Shepard, My Dear Killer) invites a dozen friends and family members to spend the weekend at her spacious country estate. As only happens in the movies, no one’s calendar holds a conflict, so everybody shows up. Why has she gathered them? To find out which one of them murdered her husband! What’s on the menu? Exposition!

In classic Agatha Christie fashion, every guest has a motive; Lisa simply needs time on her dime to suss out the culprit among the parlor of suspects. Also in classic Agatha Christie fashion, that task becomes markedly easier as they begin dying — but not until after the one-hour mark, oddly enough. You could call this Spanish-language film And Then There Were Ninguna. Croquet is played; “elegant gigolos” are discussed; affairs are consummated; allegations are hurled. Eventually, one of them sticks.

Featuring Paul Naschy in a small role as part of Mrs. Mandel’s help, The Killer Is One of Thirteen comes from Javier Aguirre in the same productive year he and Naschy collaborated on Count Dracula’s Great Love and Hunchback of the Morgue. Although by no means a bust, this project is the least of the three, with Aguirre unable to crack the code of how to handle such an expansive cast; we get to know only a few characters — and barely at that, with the possible exception of Shepard’s widow — while others don’t even register from scene to scene. The film is no great mystery, but we’ll call it good enough. —Rod Lott