Gideon was a genetically modified Leaellynasaura that was created by Dr. Gustavus in a hidden lab in Jurassic Park. Like the other Leaellynasaura created by Gustavus, Gideon had heightened intelligence and dexterity. When InGen scientists Abby Nakajima and Derrick Hoyle snuck into Gustavus' lab to attempt to find out what he was working on, they encountered several of his mutated specimens, including Gideon. When Gustavus discovered them, he introduced them to Gideon and some of his other creations while explaining exactly what he was doing with them. He then threatened the pair with his pistol, but they managed to escape. By the time Derrick and Abby returned to Gustavus' lab after losing the mad doctor, Gideon and all of the other animals had escaped from their confines. Gideon was fiddling with the pistol that Gustavus had dropped earlier, resting his claw on the gun's trigger. When a bloodied and battered Gustavus returned to the lab and began threatening the pair with his machine gun, he and Abby both tried to convince Gideon to hand the pistol over to them. When Gideon began handing the gun to Abby, Gustavus angrily shouted at the dinosaur, causing the startled Gideon to press the trigger and shoot Gustavus in the chest, killing the dinosaur's creator. However, the stormy weather caused the cliff holding up the lab to break and, while Derrick and Abby managed to escape, Gideon and all of the other genetically enhanced dinosaurs fell into the sea with the lab, where they drowned.