Season 4 premiered on September 1, 2008 and follows on from Season 3. Michael seeks revenge for Sara's death and finds out that she is alive and that the head given to Lincoln was from someone else. Michael also learns the truth about Whistler, that he has secretly been working alongside Mahone to take down the Company. Whistler's life is taken shortly after this by a Company Operative. It is learned that the inmates rioted at Sona and Bellick, T-Bag and Sucre escaped during the chaos. Donald Self (Michael Rapaport), a Department of Homeland Security agent, recruits Michael and Lincoln as well as Sucre, Bellick (Wade Williams) and Mahone for their help to bring down the Company in exchange for their freedom. Also joining the group are Sara, who escaped from Gretchen which resulted in Gretchen's own captivity by the Company, having failed to secure a valuable item, and Roland (James Hiroyuki Liao), a hacker who was assigned to help them after getting arrested for identity theft. Together, they devise a plan to retrieve data from the Company that will help to destroy the Company. In the meantime, Wyatt (Cress Williams), an agent from the Company, attempts to track Michael and Lincoln down and T-Bag heads North to the US with the "Birds" book in his possesion. He is in the process of stealing Whistler's plan.