Multiple realities(covers information from several alternate timelines)
Ensign Walsh was an engineer who worked aboard the NX-class starship Enterprise NX-01 during the vessel's search for the Xindi weapon in 2153.
Walsh served on the aft bridge of Enterprise when the ship entered the Delphic Expanse and was attacked by three Klingon Bird-of-Prey under the command of Duras, son of Toral. (ENT: "The Expanse")
In November 2153, Walsh was on duty in engineering when he was taken hostage by a group of Triannon who took over the ship. (ENT: "Chosen Realm")
In an alternate version of 1944, Walsh assisted Commander "Trip" Tucker to repair one of the starship's shuttlepods, which had been damaged in an attack by a squadron of P-51 Mustangs. In order to repair the craft, the shuttlepod required a new EPS conduit. Tucker asked Walsh to retrieve a replacement conduit from the injector assembly in engineering. (ENT: "Storm Front")
He had a meal in the mess hall. (ENT: "Terra Prime")
Ensign Walsh was portrayed by regular background actor and Paramount set security Duncan K. Fraser.
In the final draft script of "Storm Front", Walsh was instead called "Jenkins", referred to that way once, in dialogue.
Duncan K. Fraser received no on-screen credit for his appearances as Walsh except for the episode "Bound", where he was credited as "Crewman #2".