Crewman Nagle was a young male Bajoran who served as a waiter on the UFP Poseidon. He had previously worked in maintenance on the cruise liner during its last two runs.

He was present in the main lounge of the Poseidon when it ran into a magnetic strand which disabled most of the ship.

Because of his knowledge of the ships venting system he was drafted to serve as a guide by captain Kathryn Janeway after another Poseidon crewmember pointed out Nagle as one who might know more of the ships engineering systems. At first Nagle had been reluctant to do so but his commanding officer, captain Bingham deferred to Janeway in the situation, meaning that Nagle had to join her. Nagle warned Janeway and her party that entering the venting system was very dangerous because it was filled with gravity wells, and possibly broken conduits that could fill the vents with plasma. Nevertheless, he was brave enough to attempt to guide them to the ships engine room, an action that impressed Janeway.

While climbing up a shaft he was the first to notice that the air flow changed direction. It gave the party enough time to, at least, partially brace themselves as gravity reversed in the shaft.

He did however open the hatch of the shaft too quickly, without even checking if the atmosphere in the corridor had not been breached, it had not, but nevertheless he almost killed the entire group.

Upon reaching the engine room and discovering that the USS Voyager had already responded to the Poseidon distress call and secured the ship, Nagle was not afraid of showing his annoyance and displeasure at Janeway for needlessly drafting him into the dangerous trek across the ship.

Nagle remained on board the Poseidon after Voyager left, presumably to travel with the Poseidon to the nearest repair base. (MLN: "Chaotic Cruise")

In the movie "The Master and Commander: The Far Side of the World", which takes place on a Brittish naval ship, there is a character who is also named Nagle, and whose rank is also crewman. It is unknown if the name is a coincidence, an intentional joke or small tribute to the movie.