They played real-life chess so they can go to the place where the sorcerer's stone is. Then Hermione and Ron is left alone because Ron got wounded and Hermione needed to guard him. So Harry went alone to go to the place where the sorcerer's stone is. When Harry went to the place where the sorcerer's stone is, he became surprised because he saw Professor Quirrel there.
The mirror of erise showed that someone put the sorcerer's stone in Harry's pocket. When he touched his pocket, it's really there. Professor Quirrel then asked what he saw. He lied and he told him that he saw him and D u m b l e d o r e shaking hands. But Professor Quirrel knows he's lying. Then Professor Quirrel removed his turban and Voldemort's face is revealed. When he touched the sorcerer's stone and Professor Quirrel, Professor Quirrel's skin burned because of the power of the stone.