in the season premiere, michael has tracked down gretchen and whistler to los angeles as he prepares to avenge sara's death. when michael has both gretchen and whistler at gunpoint, gretchen reveals to him that she had lied about killing sara tancredi. unsure whether or not to believe her, michael contacts lincoln and then bruce. when both michael and lincoln get arrested, don self tells them that they can either bring down the company and get scylla (a key card that stores every bit of information about the company – essentially their "little black book") or go to jail. they refuse and are bailed out by bruce. bruce takes them to sara where michael and she joyfully reunite. a hired assassin named wyatt eventually hunts them down and tries to assassinate them at sara's safe house. it is then that michael and everyone decide to take self's offer. they are joined by mahone, sucre, and bellick in their mission. to blend in with the crowds, michael gets his tattoos removed via laser surgery. throughout further episodes, michael is seen to be experiencing health problems, getting nosebleeds and suddenly clutching his head in pain. he hides these from lincoln and sara, but in the episode "safe and sound" michael experiences a bloody nose that he could not hide from lincoln. michael tells his brother "it's not a big deal." and lincoln replies "it was a big deal when you were thirteen..." it appears that michael shared the condition with his mother; she during her childhood had frequent nosebleeds that stopped but resumed shortly before she died at the age of 31 of a brain aneurysm. this death was a discrepancy that was never directly explained when she turned out to be alive later in the season, however based on a statement by the general regarding prior results of a surgery, and later information revealed about michael's mother, the explanation of the discrepancy is subtly implied. michael is experiencing nosebleeds for the first time since 13 and is about to turn 31. in the episode "the legend", michael is no longer able to hide his sickness as he collapses in the warehouse. sara takes michael to the hospital where the doctors diagnoses him with a hypothalamic hamartoma, advising that emergency surgery is required or he might die.