The BAU search California's Angeles National Forest after a number of bodies mysteriously turn up in the mountain lakes there. Also, Rossi struggles with an agonizing decision regarding his ex-wife.
When Barney suffers from the world’s worst hangover the morning of his wedding, the gang tries to figure out the far-fetched ingredients to concoct the Stinson Hangover Fixer Elixir.
The BAU feels the heat when they head to the famous Santa Monica pier to investigate burned bodies left near there, and Rossi reconnects with his former Marine sergeant from Vietnam.
J.D.'s ego gets in the way of the learning process when Elliot continually outperforms him.