The story begins with Lara narrating her current situation.
2000 years ago, in Central America, there was a battle between a warrior called Totec, the Guardian of Light, and an evil god called Xolotl, the Keeper of Darkness. Totec's army was wiped out when Xolotl used the Mirror of Smoke to unleash his army of demons. Totec found a way to imprison Xolotl within the Mirror of Smoke, and he then turned to stone to become an immortal guardian, just in case Xolotl was ever free in the world again.
In modern day, Vasco, a warlord, steals the artefact from Lara and unknowingly releases Xolotl. Totec animates to life and tells Lara that they must stop him before the light of dawn. They follow him through temples, fighting evil demons and T-Rexes, until a final battle with him. Xolotl is defeated and returned inside the mirror, and Totec turns back into stone to guard the mirror once more, all in time before the sun rises.