Tom Card (Season 6, Episode 2) has set the wheels in motion for Fiona's release, but the CIA won't help unless Fiona becomes their asset and aids in the apprehension of her arms supplier.
Meanwhile, in order to get Rebecca's help in taking down Anson, Michael has to help remove Anson's leverage. Rebecca's brother is in witness protection; hiding out from a crime family he testified against, but Anson has the power to expose him to his enemies. Michael's only option is to convince the crime family to call off their search for Rebecca's brother.
When the CIA needs Michael's help taking down Fiona's arms supplier, he's torn between his two missions. If Michael fails at either, Fiona is doomed to spend the rest of her life in prison.