'Married At First Sight' 2019: Heidi and Mike's final vows promise big shock

After a jubilant real-life proposal (thank you, Jules and Cam) and a devastating breakup (we're still crying, Ning and Mark) it's time for Heidi and Mike to make their final vows on Married At First Sight.

Heidi, 38, and Mike, 44, are an interesting and complicated couple.

They were physically and sexually attracted to each other from their wedding day, but as early as the honeymoon cracks started to appear in their relationship, when it became apparent that they weren't on the same page emotionally.

Mike seemingly doesn't have time for Heidi's deepest fears and thoughts. Heidi nit-picks at every small thing Mike does wrong, and has a tendency to blow things out of proportion.

They have both been given endless advice on how to make their relationship work from the experts.

It all comes to a head tonight.

In the promo for their final vows, there's a lot of emotion from Mike.

"This is why I'm single at 44," he cries.

"If he hurts me, it will destroy me," Heidi says in a voiceover.

In his vows, Mike acknowledges, "Heidi, I struggle to make you happy." And then, in a voiceover, "I just hate saying goodbye like this."

It could really go either way for the experiment's most tempestuous couple.

Then, after Heidi and Mike's final vows, we'll be treated to the most explosive reunion dinner party in MAFS history, before the brides and grooms sit down to relive the experiment -- which includes seeing footage they've never seen before.

Bring. It. On.

Married At First Sight Season 6 airs tonight at 7:30pm, Sunday at 7pm and Monday at 7:30pm on Nine. Catch up on exclusive interviews and gossip at 9Honey Celebrity. Missed an episode? Get your Married At First Sight recaps here. MAFS obsessed? Tune into 9Honey's weekly chat show, Talking Married, where you'll get the inside scoop on every episode. For more on MAFS, including past episodes and behind-the-scenes clips, head to the official site.