A Love So Dark - Fatal Fidelity, #4

The visceral conclusion to the Fatal Fidelity series. After Justine and Campbell's beachside vacation is interrupted by the FBI, Campbell is arrested for murder and arson. The evidence leaves them in an impossible position: either take the fall for an assassination they didn't commit or confess to a killing they already got away with. When an aggressive federal agent starts uncovering Campbell's secrets, it's only a matter of time before the other bodies they've buried come back to the surface.
With Campbell behind bars, Justine can't prove their innocence, but she can take matters into her own hands. She just has to commit the perfect crime-before they both lose everything.