Set the whole deck with the soul mate in the same place. It doesn't matter the order.
Then you will have two piles with the soul mates in the same place.
Put the two piles together.
Have the spectator pick a card.
Have them look at it but you don't look. And cut the deck at where they took there card from.
Look at the top and bottom cards.
Find the soul mates in the deck and there will be one card between them.
That will be there card.
To reset the deck just set there card at the bottom.