How I Met Your Mother season 9, episode 19, “Vesuvius,” airs tonight at 8 p.m. ET on CBS. Barney faces the most difficult decision in HIMYM history: his wedding suit.

Barney got over a brutal hangover on last week’s surprisingly poignant HIMYM. Now tonight at 8 p.m. Barney must face an even bigger crisis: choosing a groom’s tux out of his extensive suit collection.

The preview that CBS released teases another even more important bit from the episode: the return of Christin Miloti as the Mother. As season 9, and the entire HIMYM series runs down, Miloti has appeared in more and more episodes. It looks like in this episode, future Ted will be telling future Mother a story, involving “intrigue, betrayal and lamps!”

Meanwhile, Lily and Robin have a fight. We don’t know what it will be about but the episode title “Vesuvius,” named after the powerful volcano, suggests that it could be a brutal one.

To lighten the mood, the gang also will watch a movie Ted has forbidden them to see. The Wedding Bride, perhaps?

How to watch ‘HIMYM’ season 9 online

CBS does offer a free, legal replay of How I Met Your Mother episodes on their website to watch online the morning after an episode airs. Their video player can get a little spotty, but it’s hard to beat that low, low cost of free. iTunes also offers How I Met Your Mother episodes for purchase, and a season pass option as well.