Melissa McCarthy’s latest balls-out comedy firecracker suffers from the same flaws as her previous outings, The Heat and Identity Thief: The overall script is lacking, expecting its star to fill in the holes. Which would be more acceptable if McCarthy and Ben Falcone hadn’t written it. Whoops. Regardless, Tammy—about a woman who gets fired, leaves her cheating husband and goes on a road trip with her grandmother (Susan Sarandon), culminating in a lesbian 4th of July party—has an incredible first 20 minutes, as Tammy spirals down, McCarthy unafraid to hurl herself under the pile of indignities. The movie’s tonal clashes likely come from first-time director Falcone finding his feet and the script’s attempt to counter its brash humour with more human moments between McCarthy and Sarandon (Grandma’s a raging drunk). Mark Duplass, Budget Mark Ruffalo, is along as an appealing enough but wholly unnecessary love interest; the smallest roles are packed with talent—Toni Collette, as the mistress, doesn’t speak a full sentence, and Sandra Oh has a couple scenes as the femme partner of Kathy Bates. It drags and it befuddles, but like most McCarthy properties, Tammy sings when she’s onscreen. Worth the bumps.