Cloak

Gibbs sends DiNozzo and Ziva to try and break into a top secret military facility, telling them that it is a test of the facility's defenses. After being caught halfway through the act, it is revealed that the facility is in fact all a hoax, and that halfway through their attempt to break in, the mole set off the fire alarm and managed to gain access to the main computer, which had its keyboard laced with a radioactive substance. After returning from the operation, the director explains to the team that one of them is the mole, and explains about the radioactive trace. He scans the hands of Tony, Ziva, Gibbs, and Ducky, and then goes to scan the hands of Abby. When he does the counter ticks, and Abby is placed into custody. Subsequently, Abby is revealed (though not to Lee) to have been in on the plan to catch the mole from the beginning. The team is monitoring Agent Lee to see if she contacts anyone, believing that the team no longer suspects her. After Lee makes a mark on a newspaper dispenser, she is brought into custody. Lee reveals that she was forced to trade secrets, because her daughter had been kidnapped. They let her go, and the episode ends with Gibbs concealed in the back of Lee's car saying "Looks like we're working together."