When he became an agent for Homeland Security, Jason Donovan no doubt had every reason to believe that he'd be assigned to perfectly human casework. Five years in, he learned that he had been wrong.
The woman he knew as Tara, whom the whole of DHS had been working on for as long as he'd been with it, whom he personally had been safeguarding for unknown reasons for most of that time, turned out to be an angel.
No, literally, an angel. He'd been told there was a threat to her personal safety, and that in turn her safety was the country's safety, and never for a moment questioned how or why. That wasn't his job. He spent years believing that he could have explained it to anyone, easily, if he'd needed to, if he'd been allowed.
He developed an interesting relationship with Tara. He knew romance was off-limits, but he could never shake for a minute, from the very first moment that he'd been introduced, that they somehow had an intense connection that went beyond any conventional understanding he'd ever had. He wrote it off for most of that time as a duty of his professionalism to overlook.
For months, though, before he found out who and what Tara actually was, Jason had been increasingly unable to succeed in that regard. He never crossed the line, was never inappropriate, but he began taking his duties to a whole new level. He was rarely anywhere but directly at her side, and he had no complaints at all about that. She didn't seem to mind, either, but then she seemed to be at peace with the world, at all times, no matter what happened.
When he finally learned the truth, Tara immediately changed tacks with him. She expressed to him in intimate terms how much his devotion had meant to her, how she could never say anything about her own feelings to him, and how much it'd hurt. She'd chosen him personally.
He was told that he would need to escort Tara out of the country, that she had become a target of terrorists who resented that the angel had come to America. She only trusted him, and now the people entrusted with her protection planned to put them in the most remote region on earth. Jason decided that it was an easy call to continue his service.
He found himself in a secret base, and an even more secret space shuttle, the last operational one under American control, and told that he'd be going with Tara into space, where they would all be safe, where Tara could continue her duties, and so could he. She kept the world safe, and he kept it safe for her, only now that would be on the moon.
It was many years before they finally acknowledged their love for each other. Jason Donovan discovered that he no longer aged. As long as he could remain at Tara's side, he was fine with that.