Ted and Robin are surprised to run into Barney when they volunteer at a homeless shelter on Thanksgiving.
Determined to speak with Sara, Michael enlists T-Bag's help to get to the only phone in Sona; Lincoln tries a daring rescue; Whistler comes clean to Michael; Bellick makes an enemy while trying to get back on his feet.
A professor from Lewis' past tips off the BAU to an alarming number of overdose deaths of patients who just completed rehab.
In an attempt to save the world, the team searches for Gravitonium.