It begins with an 18 Year Old,Marcus Bledsoe has been studying fossils & mythology. He keeps trying to get over of being traumatized after his mental ill sister,who thought that they're coming for her,kills herself & their parents. Later,He notice a picture of a missing Police Officer.
He accidentally hit the biker's van and being chased by them. As he ran into the woods,Marcus ended up in the cave where he ended up being pulled into a portal to a New World. Wondering in the desert,He finds the corpse of a missing cop. He is suddenly attacked by the Diablos,a horned subterranean monster. He was quickly saved by the Huntress & her cat like companion,Palico.
They explain to Marcus that this world is crawling with monsters. He soon learns that the portals are created by the Sky Tower. Marcus & the Huntress manage to kill the Diablos. They reaches an oasis populated with Apceros,a tortoise-like herbivores. Suddenly,a Rathalos,a fire-breathing wyvern,flies by and causes a stampede.
Marcus,Palico,& the Huntress are rescued by a group of hunters led by the Admiral,who explains that the Sky Tower was built by the first civilization to travel between worlds,using the monsters to protect it. Marcus notice that the Hunters has all kinds of stuffs they found and finds his sister's ID that she lost. This makes him realized that She has been there,being hunted by the monsters and then escaped before it led her into a Murder-Suicide because she was afraid that the Monsters will be coming for her.
As the Huntress comforts him,Marcus agrees to help kill the Rathalos so that he can return home. In the ensuing battle,Marcus falls through the portal,returning to earth. He was later confronted by the vengeful Bikers,who are hunting him. Marcus notice the portal didn't close in time and the Rathalos emerges,killing the bikers,and wreak havoc in the town. The Military open fire at the monster,but gets killed. Marcus manage to slow it down long enough for the Huntress to slip through the portal and deliver the fatal shot.
The Admiral approaches Marcus and that as long as the portal opens,there will always be the threat that monsters will pass through the earth. Marcus will find a way to take down the Sky Tower.