Post-movie, Graves is discovered by muggles. He's been tortured until he's so addled he can't communicate well, and he certainly can't stage an escape from the muggles.

Meanwhile, the doctors are baffled because their patient shows no outward signs of physical harm, yet he has loads of "internal distress". They do what muggles in the 1920s did best-- give him many, many enemas.

Bonus points for Graves eventually being found by Tina, followed by plenty of semi-traumatized grumbling from him when she takes him to a proper, "non-barbaric" healer.