House Season 6 Episode 11 (01/25/10)
The patient of the week on this episode was a psychopath. We mean that literally. As diagnosed by Thirteen, Valerie couldn't feel any actual emotion, as she slept around, manipulated her husband and broke any rule she could to get a promotion at work.
Because Thirteen seemed clearly taken aback by her, Valerie went out of her way to make life miserable for the gorgeous doctor. She even called in an anonymous complaint of sexual harassment. But Thirteen eventually played a key role in the patient's diagnosis.
By the end, she dumped her husband, but actually showed signs of feeling some emotion.
The same could be said for House, whose storyline picked up on his stay in the mental hospital. While there, he had to write a letter of apology to someone. As Wilson pointed out, he chose an old med school classmate over Cuddy because it's easier to apologize to someone you have no feelings for. In this case, House had stolen this classmate's paper on time in order to see if his professor would grade him differently.
Now, the classmate had tracked House down. Turns out, he's a cashier as a grocery store and initially convinces House this is due to his failure in that one class they shared. House feels guilty for his actions, especially when he learns the man is getting evicted from his house. As a result, House writes the guy a check, but he finally comes clean: he got an A plus in the class he and House shared. He lost his medical license due to shady practices and that's the reason for his problems in life.
Despite this admission, House still sneaks over to the guy's house and slides the check under his door. It seems as though he honestly wanted to make amends and truly felt sorrow for this individual, two traits the old House never really experienced.
Thirteen and Foreman also got along better than ever by the time the episode ended. They'll likely get back together at some point.