So I'm writing this script that has a main timeline and bursts of flashbacks, and one of the characters spent years keeping the secret of another, but I feel their reasons are a bit weak. So here goes: A famous author is raising his child alone, and sexually abuses her. She murders him when she's 10 years old, in what appears to be natural causes, but... a kid that age is not perfect with forensics. A 44 year old cop who is in the investigation figures stuff out, but chooses to remain silent. The kid has a feeling that cop figured it all out, but he's quiet, so she remains quiet as well. Now, the guy IS slightly crooked, and remains crooked later on even after he's out of the police force (if he wasn't crooked he wouldn't hide something this massive). But why does he hide her secret? He does it because deep down he's a nice guy who cares about her, but she IS a stranger, at least at first. Note: It can't be because he wants to extort the kid or anything like that. They start sharing a genuine caring bond years after the murder.