The team treats a teenager who doesn't know that he has genetic mosaicism; Wilson and Cuddy think something is wrong with House when he starts acting nice.
Meredith's dishonesty is revealed, leading to unexpected consequences for her and others; Cristina is forced to choose between her relationship and her career; the new chief resident is chosen.
Sam finds that Meryl is not the forgiving type after his project with Ralph turns into a circus.