Ted's friends try to help him woo his perfect woman from his college days but Barney and Robin spoil his big chance. Will he still get his girl? Elsewhere, Marshall reads a letter that he wrote as a teenager with a list of things that he wants to achieve as an adult. Marshall tries to rectify his life choices but is overwhelmingly disappointed in the career he's chosen.
Barney approaches a personal milestone: sleeping with the first woman he hits on seven nights in a row. However, is Barney using this to cover a bigger problem? Elsewhere, Lily and Marshall realise that they've been using the same toothbrush, Robin waits to hear back from a date and Ted insults one of his students.
A new lead in a cold case requires Lisbon to postpone her plans to relocate to Washington. This gives Jane time to wake up to his feelings for her and decide on a course of action.
In the conclusion of the two-part episode, the Philadelphia PD and the FBI continue their joint operation to catch the serial killer before he strikes again.
In the first part of a two-part episode, the team begin a joint investigation with the FBI regarding a serial killer who has reappeared after 27 years of silence.