Sometimes the movie is a little too slick. Some of the characters, such as Sean’s girlfriend (Jacqueline Byers) and the FBI agents who begin to believe Sean’s story, are underdeveloped. But Tennant, excellent as a creep, and Sheehan, who is appealing in his helplessness, provide the necessary depth.

The filmmaking itself is suspenseful, classic horror filmmaking, with plenty of jump scares and ominous camera movements. But where the film succeeds most is in its realistic use of technology.

A few plot contrivances aside, the unspectacular Bad Samaritan is tense and disturbing enough, and worth its weight in popcorn.

It’s all thoroughly unpleasant, but then, that’s what audiences for this kind of movie want from the experience, so consider it a success of sorts.

This comparatively low-budget effort represents a marked improvement from Devlin’s debut theatrical feature, Geostorm, which was among last year’s very worst films. He’s graduated from painful tedium to an acceptable means of killing two hours. One step at a time.