The character's superpower is ferreting out the truth. He uses his ability to detect lies to do it. That's what separates him from his protegée.
That throws an interesting light on the business with his partner's husband (I love her character, btw) - he just couldn't leave those lies alone and it didn't really get him any closer to the truth.
but it did, didn't it? He thought that he was having an affair, but it turns out that he was doing coke.
He found out that he was in rehab because Dr. Foster told him. He knew that Mr. Foster was lying, but not about what.
Question is--was Mr. Foster lying to his wife when Lightman detected the lie, or was he lying for Lightman.
And Dr. Foster told Lightman to butt out when she explained the sponsor (which, honestly, the cross-gender sponsors that are only on TV chap my hide a bit). So, if he respects that, he won't really find out for sure.
Q&A with NF about Castle on ew.com
House: The patient has an evil hand!
Woah. Did not see that coming.