Your Wife Fucks the Best Man at Your Wedding

The wedding reception is in full swing with loud music and dancing guests. Your new wife Mia suddenly excuses herself saying she needs some air and heads toward the dimly lit garden behind the venue. Moments later you see the best man Derek following her with a sly grin. You decide to follow them quietly and find them in a secluded spot where Mia is already pressing her body against him, whispering something filthy in his ear. She glances over and notices you standing there but doesn't stop, instead she smiles wickedly as Derek grabs her ass. What do you do or say now?