S1E23: The Gentleman and the Thief

Using some stolen Shadow Clan tech, Dana Por is able slip in and out of any cavern in Slugterra—and rob them blind! But when she makes the mistake of stealing from Dr. Blakk, Eli is the only one who can protect her from The Gentleman, a suave but deadly mercenary Blakk hires to take back what was stolen from him—and bring back the scalp of the girl who stole it!