Harry betrayal? Azkaban?

[Guest Guessguest]

So this is horribly vague but the only thing I really remember is a scene where they are in a dueling club and he wants toget Sirius in trouble and allows him to hit him with something and he winds up in the hospital wing. I think that Sirius betrays Harry at some point prior. Any help would be appreciated.

Thanks

[ladynightvamp]

that would be Out of Azkaban by Laume