Moukarbel, Chris

A biographical look at the Philadelphia rapper Tierra Whack takes a hard left turn.“Cypher” is a fakeout film disguised as a real music documentary. For a while, you believe it will chronicle the rapper Tierra Whack’s rise, from teenage Philadelphia poet to Grammy-nominated hip-hop artist whose fans include Cardi B and Billie Eilish.As the film eases you in with a cushy setup, Whack jokes that it could be completely derailed, ending in jaw-dropping fashion — which it does. “You could die, I could die and then we can’t shoot anymore,” she says, amusing even the director, Chris Moukarbel. Then things get weird. When Whack and her crew wind down at a late-night diner after a Chicago concert, she meets a fan desperate for her to watch a video that you know she shouldn’t watch. Afterward, she is still the real Whack, but in a very different movie. Adding to the sinister shift, she spots an ominous radio on the set of Beyoncé’s “Black Is King” film (Whack, who has a cameo, was actually there).A cunning experiment in cross-genre filmmaking, “Cypher” is all fun, games and hagiography until it’s not, effectively deceiving at every conspiratorial turn. The less you know about how this meta spine-chiller comments on the dark side of celebrity surveillance, the greater the thrill of discovering the “real or not?” events as they come. I’ll say this much: When “Cypher” stops masquerading as a sincere artist bio and ends up where you never thought it would, the film certainly gives new meaning to “behind-the-scenes access.”CypherRated R. A few expletives. Running time: 1 hour 21 minutes. Watch on Hulu. More