Nathan Murphy is a main character in Leprechaun.
Nathan's first appearance in the movie is when he, along with his brother, Alex, and their friend, Ozzie, arrive for a paint job at the recently bought house of J.D. Redding. During this, Nathan ends up spilling his can of paint filler when J.D.'s daughter, Tory, bumps into him. They have a small conversation, during which Nathan challenges Tory's bravery, which is enough encouragement for her to stay at the house.
After a while, Nathan assists Tory with the paintwork when he then leaves to presumably get more paint. When he comes back, Tory gets scratched on the knee by the Leprechaun (which Ozzie said to have terrorized him earlier in the house's cellar) and J.D. gets bit on the hand a little while later. Nathan and Tory, along with Alex and Ozzie, take J.D. into town to get him to a hospital.
The four then decide to stay in town for a little while, during which Nathan takes Tory to a diner, where she complains about the meat menu. After reuniting with Alex and Ozzie, they head back to the house, where the Leprechaun finally attacks them. First, Nathan gets his foot caught in a beartrap, Ozzie's ear gets bitten by the Leprechaun and their paint truck gets toppled over by a hand-made vehicle the Leprechaun is driving.
After calling the police, the four are stuck in the house until Ozzie admits that he and Alex hid the Leprechaun's gold in the well. Tory goes out to get it and gives it to the Leprechaun, believing that it will now leave them alone. Unfortunately, one coin is missing (which Ozzie had accidentally swallowed earlier) and the Leprechaun attacks them once again.
After getting attacked further more, Ozzie suggests that they go to Dan O'Grady for advice on how to kill the Leprechaun. While Tory goes to drive to the retirement home that O'Grady resides now, Nathan, Alex and Ozzie distract the Leprechaun by tossing their shoes at it. After Tory drives away, Nathan bunkers down in the house with Alex and Ozzie.
When Tory gets back with the news that 4-leaf clovers can kill the Leprechaun, Nathan and Ozzie help her find one in a patch of clovers near the house. Before they can do so, the Leprechaun attacks them once again, causing them to split up. When Tory is cornered by the Leprechaun, Nathan shoots it with a shotgun, giving them a chance to run away.
Tory eventually finds a clover, but the Leprechaun attacks her and almost succeeds in killing her when Ozzie informs the Leprechaun of the coin in his stomach and then runs outside. Tory then gives the 4-leaf clover to Alex, who then sticks it in a wad of gum and shoots it into the Leprechaun's mouth with a slingshot.
The Leprechaun then falls into the well, but it tries to come back out. Nathan prevents this by knocking the Leprechaun back down with the shotgun, pours gasoline into the well and sets the well on fire with a match. This causes an explosion which defeats the Leprechaun once and for all.