Sam's frustration at being unable to find a therapist and Casey's anxiety about going to a new school spark a blowup between the two.

Casey feels less than welcome at Clayton. Sam asks Paige to spell out the rules of their "casual relationship," while Doug sets boundaries with Elsa.

A peer group meeting leads Sam to an important decision. Detention with Izzie shows Casey they have more in common than she thought.

Zahid teaches Sam to lie, while Elsa practices being honest. Evan helps Casey get over an embarrassment. A doctor visit forces Julia out of denial.

In peer group, Sam realizes he needs to manage his own money. Doug gets advice from Megan on dealing with Elsa. Evan meets Casey's new friends.

To prepare for college life, Sam sleeps over at Zahid's. Sam's $700 loss reunites Doug and Elsa with Arlo's parents, former friends of theirs.

Casey tells Izzie what Nate did. Sam tries to figure out which colleges to apply to. Doug discovers a need to educate first responders about autism.

Sam loses his portfolio for his art school application and panics. Megan gets flirty with Doug, who makes a decision about Elsa. Julia calls Miles.

Ignoring Casey's wishes, Elsa throws her a big birthday party, while Sam insists on following a decade-old birthday ritual. The bartender haunts Doug.

Cruel yearbook comments show Sam who's got his back, a favor he repays at graduation. Feelings for Izzie confuse Casey. Elsa asks Doug a key question.

An ethics professor pushes Sam to his limits. Elsa keeps an eye on Doug ... and Megan. Casey considers her future and encourages Evan to do the same.

While Sam and Casey face friendship dilemmas, Elsa uncovers a charming surprise, and Doug makes an unexpected decision.

Casey's demanding schedule starts affecting her grades, while Sam seeks out some extra credit himself. A chance run-in revives old suspicions for Elsa.

Sam seeks a worthy caretaker for Edison. Casey tries to be supportive of Izzie, but her plan backfires. Zahid shares tough news with Sam.