“Seaside” (*1/2 out of four) was a lackluster thriller about a young woman (Arianna DeBose) who leaves home and moves to the Oregon Coast with her mysterious boyfriend (Matt Shingledecker) but soon finds that there is more to him than meets the eye and that he hasn’t been honest about his past of which they have a lurid connection. Stark and moody cinematography from Phillip A. Anderson keeps you watching for a few scenes but story meanders and is inert and you eventually lose interest. Even a key plot twist at the end is extremely subdued.