Some time before his appointment to Nublar, Robert Muldoon worked as a tracking guide in Africa. He encountered rival guides such as George Lawala and Sonya Durant. He and Lawala got into a disagreement which caused them to be rivals, but then after being saved by Lawala from an attacking Lion, causing him to regard Lawala as a blood brother.
Robert Muldoon was the game warden for Isla Nublar. He was in charge of a large security force and oversaw the dinosaur handlers. His main weapon of choice was a Spas-12 shotgun. He clashed with a scientist named Murillo over the safety of the dinosaurs. After the Tyrannosaur escapes from its paddock, it causes the Stegosaurs to stampede, causing the jeep with Muldoon and Murillo to overturn and the death of Murillo. Hunting down the escaped animals, he tranquilizes several until the Tyrannosaur steps on his jeep. However, he manages to escape with only a broken arm.
Muldoon was first encountered by the tour group when they witnessed a Velociraptor being fed a cow and devouring it. Later, he accompanied Ellie as they went to check on the jeeps after the Tyrannosaurus attack. Retrieving Dr. Malcolm, they barely managed to escape after the T-rex noticed and gave chase. Muldoon accompanied Ellie as they went to search for the Maintenance shed. Realizing they were outnumbered, he attempted to fend them off with his rocket launcher. He later Believed to be deceased after providing a distraction for the raptors while Ellie runs to get help.
However, he returns and helps Dr. Malcolm track down Ellie and Grant in Columbia. His claim is that the velociraptor was just playing and he was able to escape. He joins the group in tracking down the velociraptors that have escaped from Isla Nublar.
As he tracked the raptors through the jungle, he slung his rifle over his back and utilized Binoculars to scout the area. Upon hearing that George Lala had been killed, he swore revenge on them, and this gave him a new, personal reason to track the raptors.
He assembled a team of Indians from the village to assist them, but did not trust them. Spotting the raptors across a suspension bridge, he attempted to shoot at them. However, the natives attacked him and the group, incapacitating him and leaving Alan to have to save Ellie from a raptor.
As they pursued, Muldoon utilized a helicopter in which to covertly pursue the raptors. Upon seeing a Gorilla in the brush, Muldoon set down to investigate, clearing the way with his machete. After Ellie was abducted by a raptor, Alan had to stop Muldoon from shooting for fear of hitting Ellie.
They were fired upon by a Biosyn Helicopter, which they all barely ducked. The chopper had been ordered to kill all of them. Standing in defiance of the helicopter, Muldoon shot it down, causing it to crash. Then as they were pursued by Biosyn employees on foot, Muldoon proceeded to stalk them. Catching them by surprise, he held one of the Biosyn employees at knifepoint and forced him to shoot his comrade. Then dropping the knife, he fought against him, killing him by snapping his neck.
Later, Muldoon would shoot an attacking Jaguar that had mauled Malcolm, killing it. As they continued, Muldoon would continue to engage Biosyn, shooting down yet another helicopter. Later, Muldoon would celebrate their survival in Caracas, with Muldoon noting that the raptors were now impossible to track down.
He is later called upon by Hammond to return to Isla Nublar to try to discern the secret of the ‘Green Flame’. Some time between the events of Return to Jurassic Park #4 and The Lost World: Jurassic Park Robert Muldoon dies again, possibly. This is the only way to explain this continuity oversight in the comics, aside from the fact the comics and the events in the comics are ignored by the film makers and this carrying over to The Lost World’s comic.