As Voyager comes under attack by unknown vessels, equipment and weapons begin disappearing from the ship. The enemy is using a high-energy transporter beam to locate items of technological value and remove them. Janeway and the crew track their stolen goods to an alien world that appears to be an active center of commerce. As Tuvok and Janeway beam down to search, the Vulcan immediately locates an item with a Starfleet signature: it's Leonardo da Vinci, from Janeway's holodeck program. Somehow, the crooks got his program when they took the ship's computer processor, and the program was downloaded into the Doctor's stolen mobile emitter.
Da Vinci leads them to a room filled with other stolen goods and speaks of his "patron," a "prince" who provides him with everything he needs. Back on Voyager, Chakotay learns that a man named Tau sells weapons and technology he confiscates from passing ships. As it turns out, Tau is da Vinci's patron and Janeway gets the inventor to bring her to one of Tau's parties. She poses as a buyer and asks about computers. Tau reveals that he has Voyager's missing computer for sale.
Armed with topographical maps of the region, Tuvok returns to Voyager and reviews the information. He and Seven of Nine locate the storage facility where the processor is kept, but a forcefield around it makes transport impossible. Janeway will have to get inside the facility and initiate a power surge that will produce a signal strong enough for the transporter beam to lock on to. Unfortunately, Tau overhears Janeway talking to the ship and trains a weapon on her. Da Vinci comes to her defense and knocks out Tau, then he and Janeway head for the facility.
Once they find the processor, Janeway follows through on Tuvok's plan. The arrival of an armed guard prevents the two of them from beaming up along with the computer, and Janeway and da Vinci are forced to take escape into their own hands. They board a glider constructed by da Vinci and take off just as Tau's men begin shooting at them. Finally, Voyager is able to get close enough to the planet to beam aboard the Captain and her mentor, along with the glider that saved their lives.