CBS has released the first trailer for the new season of How I Met Your Mother, which returns with the Season 8 Premiere Monday, September 24 at 8 PM ET. Neil Patrick Harris's Barney is getting ready to finally walk down the aisle with his fiancee Quinn (Becki Newton), although don't expect the wedding to go too smoothly after a secret about Barney's past is inadvertently revealed. Watch as the marital fireworks go off before the big event.