آرٹ پرستار

Okay, so everyone knows how Sirius Black died in HP, but maybe he didn't die. Here's my theory:

After Sirius fell behind the curtain, he was sort of in a state between life and death. Lucky for him, he finds a door. He opens the door and finds himself in the Room of Requirement, thanks to the many mysteries of Hogwarts. He soon finds the passage way to Hogsmeade, and apparates, since he's not on school grounds anymore. He goes to Grimmauld Place and gets rid of the death eaters. After that, Sirius says to himself: I've gotta tell Harry I'm alive! But, he'll get distracted, so I'll do it later....