Disclaimer: I don't own Harry Potter, every character is from JKR.
Three years after the Final Battle
She had warned him and warned him. She knew he would die, she had even given that real prediction that very night, hoping she could possibly stop the inevitable. As Professor Trelawney read the book on The Final Battle, when Harry defeated Voldemort, she thought back to that moment.
Present day…
'The one with the power to destroy Voldemort will do it tonight, but he will die in helping his godfather to return to his body.' Harry stood there gaping as Trelawney gave a prediction, it was as if she knew about Sirius' problem after he went through the veil.
Sirius had contacted him over the summer. He had been brief, but had explained everything.
Harry,
I am alive. But I have a slight problem, I seem to be trapped in a different body. My body is in Grimmauld Place with me. I need you, Hermione, and Ron to help me get back to my body, I don't know exactly how, but I know I can, because if the veil transferred me here, there has to be some magic that will get me back.
Sirius
Harry sat stunned for a few seconds before going and writing Sirius a reply, and to Ron and Hermione about this strange new turn of events.