Accidental Billionaire Plus-One

All I did was mail one of my sister's rejected wedding invitations to a stranger.

A notoriously private, famously grumpy billionaire stranger.

As a joke. Mostly. (I also sent one to Ryan Gosling. Don't ask.)

But then a helicopter nearly flattens the reception tent at my sister's Hamptons wedding, and out steps the billionaire-wearing a tux, a scowl, and carrying a gift.

What?

The bride's side wants to know if he's with the groom.

The groom's side wants to know if he's with the bride.

My sister a...