“She’s not my sister,” Gretchen (Hunter Schafer) says partway through Cuckoo. The stern 17-year-old Gretchen struggles to warm up to her half-sister Alma (Mila Lieu) while on a family vacation. Gretchen, who used to live with her mom in the USA, can’t quite adjust to her dad’s new family. Her dad, Luis (Martin Csokas), and step-mom, Beth (Jessica Henwick), don’t seem pleased about having a mopey teenager. They have enough with Alma, especially when strange noises trigger seizures. Naturally, they blame Gretchen.
Gretchen’s a smart young woman, though. She recognizes right away that something’s shady in the resort area in the German Alps where her dad takes the kids to work. For one, Luis’ boss, Herr König (Dan Stevens), seems terse and pervy. Gretchen smells a rat. She whiffs another red flag when she starts her job at the front desk of the Alpine hotel König oversees. The kid’s clearly seen The Shining.
Things go bump in the night quickly. Gretchen discerns strange occurrences. Guests, for one, puke a lot. That’s not abnormal at, say, an all-expenses Cancun resort, but guests travelling solo upchuck without warning. Nobody seems drunk, but nobody looks okay, either. People in the area walk in a kind of daze. And then the sirens call: piercing, shuddering noises that trigger seizures in Alma, but make Gretchen and others undergo something akin to a temporary time loop. As actions repeat, Gretchen sees a hooded woman approach while the high-pitched violence inches closer and closer.
Cuckoo, aptly named for its transfixing call, takes a simple premise and runs with it. That’s what some of the best horror movies do. With one key setting in the hotel, a sparse cast, and an atmosphere saturated in dread, this is one lean and mean thriller.
Sound plays an unnerving role here as Cuckoo reaches some deafening decibels as the intensity mounts. Many horror flicks opt for soundtracks that signal pop-up surprises and jump scares, but that’s not the case here. The horror frequently plays offscreen with the audio cranked up so high that Cuckoo burrows a scream into the viewer’s mind like the parasite for which the film is named. The high-pitched frenzy proves disorienting, daringly putting one in the midst of this oft-kilter paradise.
Other times, director Tilman Singer (Luz) uses action happening outside the frame to ratchet up the tension. One can hear what’s happening as something wicked comes Gretchen’s way. But the mix leaves on edgy, never quite sure where the monster might appear.
Much of the drama hinges on Schafer’s performance and she totally commits to giving audiences a Final Girl to root for. The Euphoria star plays the part of the scared shitless prey when the siren first gives her call. But Schafer forcefully summons Gretchen’s strength as the young woman recognizes she’s all on her own and needs to grow up quickly. It’s a tricky physical performance, too, and Schafer lets Singer pummel her. Gretchen gets punched, sliced, beaten, and throttled, tossed around like a cat’s catch. But she’s no meek little bird. Schafer brings total Final Girl Energy and plays the badass well.
It helps, too, that she’s cast opposite Stevens, who seemingly has no bottom to his bag of surprises. His kooky, delightfully unhinged performance ensures that the monstrous siren isn’t the most sinister being in the dark shadows. He hits the part with just the right punch of slimy camp.
Cuckoo doesn’t really aim to explain the genesis of the siren stalker or Herr König’s Nazi-doctor-vibes, and the ambiguity lets the monster movie angle accentuate what’s really a very smart and perceptive take on family dynamics. As Gretchen assumes the role of protector and takes Alma under her wing to thwart this creepy boogeyman, Shafer also displays a strong rapport with young Lieu. Cuckoo tackles the role of sisterhood as the siblings become allies. Many horror films take to heart the fight to protect the family unit with parents butchering boogeymen to save their kids. Cuckoo, alternatively, leaves the parents to the side.
Instead, Gretchen learns what it means to be family here as she assumes the role of Alma’s caregiver. As she recognizes her duty, her desire to fight for her sister, calling Alma her kin gives her strength. This atmospheric horror flick ultimately becomes a moving fable about the power of chosen families as Schafer injects the Final Girl with the duty of sisterhood. Cuckoo delivers eerie blood-spattered horror that’s fun for the whole family, whatever that family may be.