“It’s my cozy room,” the man says, proudly touring his neatly arranged basement. This is where he comes to relax and be himself, surrounded by the things that make him happy: his brass musical instruments, his well-stocked bar, his Hitler paraphernalia. Wait, what? Down here in this Austrian man-cave, forbidden portraits of the Führer share space with uniforms and other Nazi bric-a-brac. You know—cozy. This is one of the many sanctuaries explored in In the Basement, Ulrich Seidl’s unsavory documentary. The baleful Austrian filmmaker (of the grueling Paradise trilogy) turns his gaze downstairs, where all the strange and dark impulses that lie beneath the civilized veneer are blossoming in full weirdness.