The Switch - Sandra Brown

From a New York Times bestselling author, a woman teams up with a NASA astronaut to avenge her twin sister's brutal murder-before the killer strikes again.
Identical twins Melina and Gillian Lloyd switch places for the first time since childhood when Melina proposes that Gillian take her place as a media escort to NASA astronaut Col. "Chief" Hart.
The following morning Melina receives terrible news: her sister has been murdered-and Chief, though innocent, is the prime suspect.
Now, with targets on their backs, they must work together to learn the truth behind Gillian's death-before they become the killer's next victims.