JJ gets promoted to temporary BAU unit chief when Prentiss is placed on administrative leave. Ten bodies drained of blood are found in a vandalized crypt in New Orleans. Another burned body is found in a crypt at a different cemetery. Barnes tells Prentiss that under her leadership, team loyalty is more important than bureau policy. The unsub grabs another victim, who wakes up and knocks out the unsub with a bedpan. But he's drugged and crashes the unsub's van. Barnes dredges up the suicide in Roswell and Stephen Walker's murder as preventable deaths on Prentiss' watch. She also accuses Prentiss of obstruction of justice for erasing Reid's confession when he was under the influence of drugs. The escaped victim explained that his abductor wore a mask and gloves. The unsub believes him to be a modern-day plague doctor, trying to eradicate those who are diseased. The BAU says he blames modern medicine for some reason. The unsub, Kevon Winters, lost his mother to a rare disease. Prentiss confronts Barnes about her ambitions within the Bureau. Reid helps the team find Winters' hideout. Winters goes into a clinic raving about his mother being contaminated. He tackles and stabs the doctor and sets her and the clinic on fire. Barnes is after those she considers loose cannons within the BAU, but Prentiss refuses to sacrifice anyone to save the unit. JJ comes up with the idea that the unsub's first kill was the person he lost to disease. Kevon's mother got sick from an apartment left moldy from Hurricane Katrina. JJ and Rossi think Kevon is going after his former landlord. He shows up to set the landlord's bar on fire. JJ tries to reason with Kevon. Rossi finds out that Kevon gave his mother a lethal dose of ketamine. Prentiss is suspended, and Barnes is overseeing the BAU.