"Wanted: Someone to go back in time," it starts.
A nutjob looking for a time-travel companion. This'll be a quirky human-interest story, right? Has to be funny, or strange, or something, right?
And so the reporter grabs two hapless interns - Darius and the dweeby Arnau (Karan Soni) - and off they go, looking for clues to who's behind the ad and what the deal is.
Sleuthing and slacker-ing ensue, but then at long last there they are: Darius, sidling up to a clerk in a grocery store aisle. His name is Kenneth (Mark Duplass), and he's throwing off vibes that are at once paranoid and weird, but also clear-eyed and kind of smart.
And he promises Darius - who is busy fixing him with a seductive stare as she casually returns a can of tomato soup to its shelf - that his "calibrations" are dead-on.
Safety Not Guaranteed goes from there, expectedly funny but unexpectedly touching, too. Duplass may be guilty of underplaying everything he's in (which is way better than overplaying), but he finds the soul of this character. He shows us Kenneth's ache, his anguish, his regret.
Johnson is acerbic and dismissive, as anyone bossing around a couple of unpaid gofers would be, and Soni is charmingly at sea, an innocent, a bumbling brainiac.
As for Plaza, she conveys self-confidence and uncertainty, and she does that eye-rolling thing that she does, too. She shows off some serious detective moves, and then shows what it's like to have fallen for your prey - to feel guilty of deception and betrayal, and to hope desperately that no one gets hurt.
Contact Steven Rea at 215-854-5629 or firstname.lastname@example.org. Read his blog, "On Movies Online," at www.philly.com/onmovies.