: Barney witnesses Marshall and Lily’s messy, honest life and decides on a single vow: to always be honest with Robin. He immediately confesses that Ted was the one who found the locket. Marshall and Lily’s Real-Life Vows
In a pivotal series moment, Robin attempts to flee the wedding and literally crashes into The Mother.
Future Ted closes the episode by noting that while no one can vow to be perfect, they can promise to love each other with everything they’ve got, because "love is the best thing we do". The End of the Aisle | How I Met Your Mother Wiki | Fandom [S9E22] The End of the Aisle
As the wedding approaches, Robin experiences a severe panic attack. Her anxiety centers on the missing locket, which she views as a sign that she is marrying the wrong man.
: Robin quickly realizes the truth—Barney’s initials are "B.S." for a reason, and he lies about everything. She briefly considers running away with Ted, who firmly refuses, telling her he is "not that guy anymore". The Meeting: Robin and The Mother : Barney witnesses Marshall and Lily’s messy, honest
Lily vows to always tell Marshall when he has green stuff in his teeth.
The episode concludes several long-running storylines as the ceremony begins: Future Ted closes the episode by noting that
Marshall promises to stop shouting at Lily while she is "dropping a deuce".