Heliotropic Series by Mardi Ballou

Serving an unjust sentence, vampire Val Cutter spots a gorgeous stranger. Contrary to his usual caution, he quickly falls for Paul de l’Astre. Paul, a prisoner subjected to cruel experiments, wants only to return to his planet -- until he meets Val. But Val could never survive on sun-worshipping Apoll’ex, and Paul will die if his sunlight deprivation continues. Forced to hide from the villain persecuting them, the men face the ultimate test of their love... moreServing an unjust sentence, vampire Val Cutter spots a gorgeous stranger. Contrary to his usual caution, he quickly falls for Paul de l’Astre. Paul, a prisoner subjected to cruel experiments, wants only to return to his planet -- until he meets Val. But Val could never survive on sun-worshipping Apoll’ex, and Paul will die if his sunlight deprivation continues. Forced to hide from the villain persecuting them, the men face the ultimate test of their love. With Paul dying, Val must choose for his lover: transformation and permanent exile -- or death? less

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... moreLife 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? less

Val, Paul, Trey and Soleil -- newly sun tolerant after exposure to Ideg Retkove’s serum -- voyage to Paul and Trey’s home world of Apoll’ex, where no vampires have ever been before. Val fears that, once on home ground, Paul will reject him. Paul wonders if he’ll ever be able to go home again. When they land, they quickly learn another vampire has preceded them and sown a path of destruction -- Retkove. The Apollans unite with the Earthlings to defeat Retkove... moreVal, Paul, Trey and Soleil -- newly sun tolerant after exposure to Ideg Retkove’s serum -- voyage to Paul and Trey’s home world of Apoll’ex, where no vampires have ever been before. Val fears that, once on home ground, Paul will reject him. Paul wonders if he’ll ever be able to go home again. When they land, they quickly learn another vampire has preceded them and sown a path of destruction -- Retkove. The Apollans unite with the Earthlings to defeat Retkove. But Retkove is not about to give up his foothold in paradise. Desperate to stay together on Apoll’ex, Paul and Val face Retkove in a final confrontation. less