Our 21st Century Cult series dives headfirst into psychological horror and comes out with one of the most claustrophobic, nerve-shredding films of the 2000s—Bug. Adapted from Tracy Letts’ stage play (he also wrote the screenplay), this fevered two-hander finds director William Friedkin (The French Connection, The Exorcist, Sorcerer, To Live and Die in L.A.) stripping things down to the bone: one motel room, two broken people, and a mounting delusion that morphs into full-blown apocalypse.

Ashley Judd gives a career-best performance as Agnes, a lonely, traumatized waitress holed up in a cheap Oklahoma motel. When she meets Peter (an always-electrifying Michael Shannon), a drifter with a haunted past and a theory about government-implanted bugs living under his skin, the two fall into a spiral of shared madness. What begins as a strange romance rapidly mutates into something terrifying, intimate, and hallucinatory—culminating in an operatic crescendo of love, paranoia, and self-immolation.