Guilty Wives by James Patterson

When Abbie Elliot and her three best friends arrive in Monte Carlo, they surrender to the sun and pool, to the champagne and private parties. For four days away from their husbands and families they're free to live someone else's life.

But in the morning's harsh light, Abbie awakens on a yacht to gunshots and police storming the boat. Two men are dead, and Abbie and her friends are the only suspects.

Imprisoned in a foreign country and separated from each other, the vacation of a lifetime has become a desperate fight for survival.