During his final day on the job before retirement, slaughterhouse worker Serge (Gérard Depardieu) takes off his hairnet to reveal a mane last seen on Ted Nugent in 1977. Dumb sight gags like this typify Mammuth, a yokel-roasting road adventure that, much like Depardieu’s other recently released vehicle, My Afternoons With Margueritte, asks little more of the actor than to play a lumbering naïf. The demands made of viewers’ eyeballs are greater: Shot on reversible super 16mm, Mammuth looks as if it were made on a first-generation smart phone. We watch Serge, exhorted by wife Catherine (Yolande Moreau), travel from one dour hamlet to another in western France on his motorbike, on a mission to gather the paperwork needed from former employers to secure his pension benefits. Pit stops include a visit to a cousin-with-benefits, inviting Serge in for a two-man circle jerk, a favorite teenage pastime. A mouth-breathing niece introduces him to the pleasures of poetry and wearing caftans. Too limp and scattershot to warrant anything stronger than indifference, Mammuth is guilty of one unforgivable act of cruelty: using poor Isabelle Adjani, who appears to have been told she was starring an Ibsen adaptation, as the bloodied specter of Serge’s first love.