In The Dark (Heliotropic #2)

Life on the run from their arch-enemy Retkove is getting to Earthling Val and former Apollan Paul. To clear his name so he and his lover can finally get a life, Val summons help -- his ex, Trey. Though they need his help, Paul isn’t crazy about the idea, getting his first taste of Earth-style jealousy.

Then Retkove kidnaps another Apollan, subjecting him to the same torturous experiments Paul suffered. Vowing to rescue Soleil from Retkove’s lab, they discover Retkove has developed a serum that makes vampires sunlight tolerant. Given a chance to procure the serum, Paul must make the choice of a lifetime: Val or the chance to return to his home planet?