Cerberus has procured the service of Kasumi Goto, the galaxy's most enigmatic master thief. In return for her help, Kasumi has asked Shepard's help on a dangerous heist to infiltrate the vault of a deadly master criminal named Donovan Hock. Gain Kasumi's loyalty on the planet Bekenstein, where Hock is throwing a party for some of the galaxy's richest and most deranged criminal minds to recover data of great importance to Kasumi... and to the galaxy at large. Includes a new squad member, mission, weapon, research upgrade, casual outfit, and achievement.
Source: The Game Website.
This DLC was made available on 04/6/2010 on Xbox360 and PC, and was later included on the PS3 release of Mass Effect 2.