"Safety Not Guaranteed" (R, 94 minutes). Three Seattle magazine writers set out to track down the man (Mark Duplass) who took a classified ad looking for a partner in time travel. Turns out he's very serious. Aubrey Plaza plays the wise-ass young writer who penetrates his paranoia. A comedy, but there's a serious undertow, kind-hearted attention to the characters, and a treatment of time travel that (a) takes it seriously, and (b) side-steps all of the well-known paradoxes by which time travel is impossible.