Snatched is the first movie starring merrily raw and raucous stand-up comic Amy Schumer since her big-screen breakout in Trainwreck. It’s also Oscar-winning screwball goddess Goldie Hawn’s first movie in 15 years. An action comedy about an ultra cautious divorced mother and her self-centered, rude and directionless daughter, Snatched is scripted by punchline smarty Katie Dippold (The Heat, Ghostbusters) and directed by Jonathan Levine (The Night Before). It ought to be a riot. Instead, the odd-couple comedy—a surprisingly violent and unsurprisingly crass play on Romancing the Stone—runs the gamut from mildly amusing to dismal.

Its setup scenes could have been Trainwreck outtakes—which, themselves, could have been Inside Amy Schumer outtakes. An oddly tamped-down, dispirited Schumer plays whiny, nasal Emily Middleton, who gets sacked from her job at a cheap clothing store and dumped by her rocker musician boyfriend (Randall Park, so funny he makes us wish he were in a better movie). He and his band are on the ascendant, he says, while Emily is crash-landing. Stuck with an extra non-refundable ticket for an Ecuadorian vacation, Emily fails to cajole any of her friends into going with her. In steps her mother Linda, against her better judgment. After that, we’re off and away on a jungle trip from hell.

Emily’s all about selfies designed to make her social-media friends jealous. She’s up for sex, adventures, booze and more sex. Linda, a former hellion, wants to repair their fractured relationship but also mostly wants to stay out of the sun and read her Cat Fancy magazines and romance novels. Emily, restless, hooks up at the hotel bar with a handsome flirty Brit (nice work from Tom Bateman). In no time flat, she and her mom find themselves kidnapped and thrown into a filthy jail cell with a resident scorpion. What lies ahead? Murder? Sex slavery? A better script?

Not much, as it turns out, except plus-size-girl jokes, ageist jokes, feminine hygiene jokes, culture clash jokes, tapeworm jokes, rape jokes and pratfalls. Lots and lots of pratfalls. Our heroines find themselves hotly pursued by a crew of kidnappers led by Morgado (Oscar Jaenada, trying to make the best of an ugly stereotype) while, back home, Schumer’s weirdo nerdy brother (Ike Barinholtz) begins harassing a U.S. State Department official (well done, Bashir Salahuddin) to initiate a daring rescue.

Meanwhile, as she and her mother are being pursued, Emily kills a couple of people and we’re just supposed to shrug it off the way she does. Whenever the laughs and action lag, which is often, a host of kooky, quirky secondary characters leap in to pad the limp premise and drag the film through its 91-minute running time. They include a genuinely funny Joan Cusack and Wanda Sykes as a pair of can-do “strictly platonic” vacationers and Christopher Meloni as a would-be Indiana Jones who helps guide Linda and Emily through the Colombian jungle.

Hawn, comic timing intact, is inexplicably underserved by the material. She’s given two assignments: Be a conservative scaredy cat, and say “I told you so.” That’s no way to treat a movie star. As if to compensate for the lack of giggles and subtext, Hawn works overtime to spark signs of chemistry in Schumer’s glazed-over eyes.

Schumer is too talented, her timing too expert, not to score some laughs. But her abrasive vulgarian shtick has already worn thin. What’s weirdest about a movie—aside from how it never finds its tone, never hits its comic stride—is how it feels as if it’s backslapping and high-fiving its self-absorbed heroine. That’s a millennial-centric theme that Schumer has lampooned brilliantly and repeatedly on her TV show, so it’s especially odd and dismaying to see her hug it here.

Schumer needs to show some range and fast. As a Mother’s Day gift to the world, Snatched is a box full of ugly.