1. I smell a rat = to suspect that something is wrong
~ Sally smelled a rat when she entered her room, she found out that she was robbed.
2. Off the hook = free from obligation
~ I'm very glad that i'm off the hook. I don't want to clean the room all by myself.
3. By hook or by crook = (by hook) by any means necessary
(by crook) to accomplish a goal, morality is not considered
~ Many rich people nowadays achieve their wealth by hook or by crook, regardless of any risks.