A diplomatic shipment is hijacked from two state department couriers on Callen and Hanna's five year anniversary. They investigate these two couriers, Diane and Roger, to see if they were responsible or not. Diane and Roger have worked together for ten years making it difficult for NCIS to get them to turn on each other. Granger is back and has an interest in the case. The blame seems to lead to their boss.
The shipment turns out to be Ephedrine. And, Sam and Callen go undercover to deliver the shipment. While there, the buyer knows Roger from the emails setting up the deal. Granger wants to bust Roger, but Sam and Callen go in and talk to the couriers. They know that Granger is wrong. Instead, Diane set up her partner to take the fall. She was the one behind the deal with her boss.