Atlas is a family man who came to Rapture in search of a better life for his family in BioShock. Guiding Jack through the wrecked districts of Rapture via a shortwave radio, he says he needs Jack's help to rescue his wife Moira and infant son Patrick, who both are trapped in Rapture.

It is later revealed, towards the end of the game, that Atlas is actually Frank Fontaine, the arch-nemesis of Andrew Ryan, who had brainwashed Jack to get to and kill Ryan.

— View the full Atlas (BioShock) overview