Midshipman first class Peter Preston was an engineer's mate aboard the USS Enterprise during its Starfleet Academy training cruise in 2285. Preston was the nephew of Montgomery Scott, the youngest child of Scott's sister. According to his uncle, he was "crazy to get to space."
That year, Preston met Admiral James Kirk during an inspection tour of the Enterprise. While inspecting engineering, Preston challenged Kirk's assessment of the ship, charging the admiral with being as blind as a Tiberian bat, if he could not see that the Enterprise was the pride of the fleet. Upon Preston's digression, Kirk noted that he was a "tiger".
Following an unprovoked attack by the USS Reliant, later determined to be led by Khan Noonien Singh, the Enterprise was severely damaged in the engineering section. Preston stayed at his post throughout the attack, even when the other trainees ran and saved one of his fellow crewmen from being trapped under the isolation door. He died from burns he sustained while assisting other engineers evacuate an area being sealed by a radiation shield. (Star Trek II: The Wrath of Khan)
Preston was played by actor Ike Eisenmann.
Many of Preston's lines were cut from the original film and video release, as were scenes revealing his relation to Scotty, but they were restored in a 1985 ABC TV airing of the film, as well as the later 2002 Director's Edition DVD and the 2016 Director's Cut Blu-ray.
In the movie's novelization, Peter's age is given as just fourteen (though Eisenmann was around 23 at the time) and also that he was six years younger than Saavik, who helps him in his studies, and on whom he has a crush. The same novelization says he had a sister who was twelve years older and already a commander.
The Constellations short story "Where Everybody Knows Your Name" mentions Scott's having shown Peter coins he brought back from planets that still used hard currency, much to the younger man's appreciation.