Lost Time - Orton D. L.

If someone took everything you live for, how far would you go to get it back?

When a faulty time machine deposits Diego at the top of a pine tree, he knows he's in the wrong place—but has no idea he's in the wrong time. Naked and shivering in the chilly mountain air, he attempts to climb down, but slips, whacks his head, and falls into oblivion. 

He wakes up inside a darkened room, crippled and disheartened, and must come to grips with the realization that he is marooned in a bleak alternate future. In this universe, what remains of the human race is trapped inside a handful of aging biodomes. With his mission failed, his world destroyed, and the one woman he loves, dead, he can find no reason to go on living. 

But Lani, the emotionally scarred doctor who finds him, refuses to let him give up, and as Diego heals, their relationship becomes... complicated. He struggles to let go of the past but is unable to get Isabel out of his head—or his heart. Just when it seems he may be able to find some measure of happiness in a world teetering on the edge of extinction...

Another note arrives from the future: Isabel is alive—but not for long…