In point of fact the plot summary unaccountably omits the key revelation that implicates Phelps as the real mole and mastermind behind the murders of Ethan's team, i.e., Ethan's discovery, after his argument with Krieger in the London hotel, that the Bible he has been consulting to communicate with Max was originally from the Drake hotel in Chicago. This points the finger at Phelps' being in the Prague safe house prior to his purportedly first meeting with the team to discuss the mission and where he incidentally mentions his stay at the Drake. The crucial relevance of this is made obvious at the time of its discovery and is later confirmed during the showdown in the baggage department when Phelps asks Ethan when he "knew,"  and then remarks "damn Gideons!"