A drug that overrides inhibitions is accidentally unleashed on a college campus. Victor, Sierra, Dominic, and Boyd are sent in by the Rossum Corporation, developers of the drug and backers of the Dollhouses, to contain the outbreak. Echo is off on another engagement, but when she sees the campus on TV, she's drawn there.
This episode went a long way toward revealing several dolls' backstories and the corporation behind The Dollhouse. As many have said, it is similar to the Buffy episode "Band Candy", but not overly similar to me.
Personality-changing episodes are usually at least a little fun, but with the dolls changing personalities every week, such an episode seems redundant. If Dollhouse wasn't finished shooting for the season, I'd think this was a quickly produced episode to explain a lot just prior to cancellation.