TimeShift

This Achievement unlocks after beating the fourth level of Act 2 on the Skilled difficulty setting or harder (Achievements stack). You will be nearing the end of the Act when you fight the rocket-pack guards on the rooftop. After the roof is clear, flip the switch on the central pillar to bring in the extraction craft and end the Act.

Upon completing the level, you will also earn the following Achievement if you have not done so already:

Excellent video walk through of the game.

Courtesy of Mmac2797

http://www.youtube.com/view_play_list?p=7CCCD268F8A07F33