TV Guide Description: Episode 4×15 “Going Under”
Following Linc’s deal with the devil, Michael has his brain operation. Linc also extracts information from T-Bag, with whom he was recently reunited. Meanwhile, Wheeler and Lang transport Mahone to prison; and as Self and Gretchen await their prospective customer, Gretchen gets a phone call from her sister that’s both reassuring and troubling. During surgery, Michael (who’s conscious) gets unlikely help in unraveling the mystery of Scylla. Westmoreland: Muse Watson.
Source: TV Guide