After the events of the first Portal, Chell has reawakened to find herself still in Aperture Science. As she attempts to escape with the help of Wheatley, an artificial intelligence, she ends up restarting GLaDOS. Facing her old enemy once more, Chell must face new concepts and traverse the deepest depths of Aperture Science, uncovering its origin and the very heart of GLaDOS herself.

In the award-winning sequel to Portal, players once again use the Portal Gun to form portals between planes and break the laws of physics - for science.