The BAU investigate a reported case of bioterrorism following a number of suspicious deaths. Meanwhile, Garcia visits her stepbrother.
Steve sees the aftermath of a gang of robbers dressed as Santa Claus; Danny tells Charlie a bedtime story involving a Christmas miracle; Junior takes a position on the Five-0 task force.
The team is taken hostage when they come across a bank robbery in progress. Meanwhile, Sylvester's feelings for Florence continue to blossom.
Joe gives Ben several tips about being a police officer; Sammy stays with Nate's family while he sorts out his marital problems; Lydia and Josie handle a drug-related murder case.