Pete and Myka return to Washington to swap the finest samurai sword ever forged with a decoy, but a sudden blast puts a wrench in their plan. They sign off as Officer Ogawa approaches, followed by Agents Mattson and Cooper, with Dickinson close behind. Things just got worse.
Dickinson recommends Pete and Myka leave D.C. while he can still let them. Later, the two are still in town, staking out a heavily guarded embassy and joined by Artie. The team enters the room to find a fused mass of materials. Artie's suspicion is confirmed - it's the work of an 'implosion grenade.' Pete correctly surmises that the thief just might be competition for other things that belong in the Warehouse.
At the hotel, Artie explains the sword is so perfect, it splits light, essentially rendering the holder invisible. Myka notices the stolen sword is missing its tsuba (a sword's hilt or hand guard), and it dawns on Artie that the sword might not work without it. While Artie tracks the source of the implosion grenade, Pete and Myka track the tsuba...to the Secret Service.
Livid, Dickinson gives Pete and Myka one more chance and a file Ogawa provided on Artie, who used to work for the NSA and is suspected of selling secrets. Artie, too, is catching up with his past. His meeting with Carol reveals that Artie once vied for her attention with another Warehouse agent named James MacPherson, the man Artie suspects stole the sword. Mrs. Frederic arrives to take the team off the case, but Artie isn't done. He heads to the Secret Service building to retrieve the tsuba, where he's caught and arrested for treason.
Pete and Myka arrive to find Artie handcuffed to a chair. He assures them Mrs. Frederic will fix the situation - and it dawns on him that the person who put Dickinson onto Artie will lead to who stole the sword, and that will surely lead to Macpherson! Before Pete and Myka leave, Ogawa arrives to reclaim the tsuba. Minutes later, Mrs. Frederic works her magic and Artie walks out a free man. She's waiting in her limousine, and sends Artie to stop MacPherson.
Later, Ogawa exchanges the tsuba for cash. The buyer connects the two pieces and disappears. Artie enters and sees Ogawa standing alone before his head is suddenly lopped off. McPherson's voice greets Artie as his gun is whacked out of his hands. Arming himself with a fire extinguisher, Artie uses the clouds of gas to track the invisible man's movement. In a quick lunge, MacPherson stabs Artie, but Artie grabs the sword. MacPherson disappears into the shadows and, as Pete and Myka tend to Artie, an implosion grenade rolls to their feet - they race for the door just in time.
Now 'safe' at the Warehouse, Pete and Myka, place the sword and tsuba on the shelves. Leena tries to defend Artie's secretiveness but Myka doesn't buy it. Witnessing the exchange, Mrs. Frederic apologizes for doubting Artie and suggests he concentrate on rebuilding trust with Myka. Artie's only worry is that MacPherson is planning something bigger.
Joanne & Eddie finish up their last interview as a Warehouse 13 cast and give a shout out to all you loyal fans!
On a rainy day at the Warehouse, Pete accidentally triggers an artifact that transforms the team into two-dimensional diorama versions of themselves, and returns the Warehouse to its original, unstable design.
Who knew Claudia had those moves?! OK, so maybe they're artifact-induced, but we're so in love with the spangles, we don't care!