Mike Rousseau works for Navy Intelligence, Kurt Halstead is a Senior Chief Petty Officer and a SEAL, and Maggie Degginger is an agent for Homeland Security. Mike and Maggie meet during an operation, and the resulting heat between them is scorching but brief. Shortly thereafter, Mike and Kurt are assigned to be working partners.
Then life throws them a curveball. Mike gets seriously hurt. Mike and Kurt finally give in to their attraction, but Kurt is double-crossed in-country and gets left behind, wounded. He manages to let Mike know that their chain of command is compromised. Mike needs help and reaches out to someone he knows in Homeland, who in turn assigns Maggie. One rescue mission, in progress.
Traitors aside, it isn't that Kurt doesn't know about Mike's previous fling with Maggie. He does. So when the three of them get together, the heat is so high, they all three just might burn.