When a nasty thunderstorm rolls through the region and threatens to postpone Lucy and Kevin's wedding, everyone scrambles to make it to the church in time. Mary barely catches the last flight in and brings a surprise guest with her. Chandler and Roxanne rush to pick up Ben and his mother who are stranded at the airport in Las Vegas, but tensions run high and a fist fight breaks out; and Matt gives Lucy some very special brotherly advice when she confesses to pre-wedding jitters.