Who Knew?

A truly terrible smell takes the trio into the basement, where they discover a dead turtle in a shoebox—and become trapped when the door blows shut. After they discover and consume a cache of cheap wine, Riley drunkenly blurts out a terrible secret: that he and Casey once slept together, violating their pact that the trio would remain just friends forever. An explanatory flashback takes them to the day of their senior prom, when Riley was dumped by his girlfriend hours before the event and Casey found out that her gentlemanly boyfriend became a beast after hours.