Episode 3 of "JAG"
s01e03 Shadow

The test of a new torpedo is carried out on board the submarine, the USS Tiger Shark. The test is overseen by the civilian software developer, Dirk Grover. This torpedo is designed to approach and then "shadow" its target until it is necessary to hit & destroy. But something goes wrong and the torpedo disappears. Grover then tells the captain that the torpedo is under his control and he will destroy a luxury cruise ship if he is not paid $40 million in gold.Lt. Rabb and Lt.(j.g.)Austin, are sent to the Tiger Shark to assess the seriousness of the threat and if necessary, negotiate with Grover to avoid loss of life.Once on board, Grover insists that he must periodically send commands to the torpedo and to demonstrate, sets off an explosive charge flooding a compartment. In the course of the invesigation, the torpedo is located shadowing a British Liner... Rabb learns that Grover really isn't in control of the torpedo unless the ship is within 4000 yds of it, so Rabb steals Grover's laptop and has Meg attempt to crack his code to deactivate the torpedo. When it becomes clear that time is running out, the crew resorts to pretend that the torpedo has turned on the Tiger Shark and that they're about to be destroyed. Grover, not wanting to die, tells Meg what the "command detonate" code is, Meg enters it & the torpedo harmlessly explodes. Only then, does Grover realize there was no danger and he is not going to be paid.