Plot summary
Morale Officer Neelix starts a ship-wide information broadcast aboard Voyager as an attempt to raise crew-morale. However, his initial reports are somewhat downbeat as he shares the news that helmsman Tom Paris (whose conduct has become increasingly erratic through several preceding episodes) is to leave the ship permanently to join a Talaxian convoy.
It emerges that someone on board Voyager has been sending information to an enemy-race, the Kazon. After Seska and the Kazon abduct Tom Paris from the Talaxian ship, Neelix suggests on his broadcast that it was Paris who had betrayed them all. Captain Janeway privately reveals to Neelix that Paris's insubordination, departure and joining the Kazon was all part of an act to flush out a suspected traitor on board. The Maquis members of the crew, including Commander Chakotay, had not been told as it was suspected that the traitor was from the Maquis. She asks Neelix to use his new journalistic role to investigate.
Neelix eventually discovers that the real traitor is Michael Jonas, a Maquis engineer. Jonas locks down Engineering, injures Neelix, and attempts to draw Voyager into a trap laid by Kazon forces. Neelix recovers and attacks Jonas, who falls over a second-floor railing and is disintegrated by plasma leakage below. Tom Paris returns after damaging the Kazon ship and stealing a shuttle. He explains and apologizes to the crew for his recent behavior, revealing that it was a ruse that he and the captain had planned to infiltrate the Kazon and flush the intruder many weeks ago. Later, Chakotay expresses his disappointment about the deception being planned without his knowledge.
Credits
Adapted from Wikipedia contributors, Investigations (Star Trek: Voyager). Paragraphs and formatting adjusted; illustrations, reference markers, block quotations and non-story material omitted.