This season's story begins with the wedding of Robin (Cobie Smulders) and Barney (Neil Patrick Harris). Back in the summer of 2012, it was a season full of love. Barney and his girlfriend Quinn, Ted (Josh Radnor) and his girlfriend Victoria, Robin and her boyfriend Nick, and Matthew (Jason Segel), Lily (Alyson Hannigan) and their son, everyone is very happy. Matthew and his wife are busy taking care of their children, and the other three couples are in harmony. However, as soon as October arrived, they ushered in the legendary "breakup season". After some tossing, Barney and Quinn broke up. Not long after, Ted and Victoria also broke up for an irreconcilable reason. Subsequently, Barney announced his engagement to Robin. What on earth is going on...