ok be ready it's gonna be ugly :
if i remember correctly the dad of michelle sexually abused ian when he was a kid for a very long time, and when his wife was pregnant and gave birth he was still raping kid ian, so ian began to think that the baby of the wife of the man who raped him was his baby too, and the baby was michelle, so he developped a twisted obsession with michelle and i dont remember what else makes him obsessed with michelle and with the idea of "taking revenge" but that's the biggest part of the probleme.

It was a two chapters global release for season 2...
Also, glad that even after wanting his revenge, Ian still can't bring himself to harm Michelle... yet.