Lily and Marshall receive shocking news that has a profound impact on the gang; Ted begins his duties as best man for an old friend's wedding.
Barney concocts a plan when his father (John Lithgow) arrives at the hotel; Ted thinks he is being framed when a wedding-related duty gets messed up.
When the gang helps Barney's mother move, they learn that she has lied to him about events throughout his life; Robin oversells Ted to a blind date.
With only a half an hour left before the wedding, Robin and Barney panic; Lily and Marshall rewrite their wedding vows.
The residents and interns treat the victims of a massive explosion at an apartment building; Mama Burke returns to collect her son's things; Lexie tries to have a heart-to-heart with unwilling Meredith.