Dimension Lapse — Nicholas T. Davis

Jeff Walker, a Martian colonist who becomes trapped in another universe after an alien encounter and crashes on another planet. He is befriended by its inhabitants,the Lingworts, and begins to live a peaceful life. When an alien force threatens their way of life, they must join an intergalactic war that they are forced to engage in. When the leader of the opposing peaceful federation steals a weapon of mass destruction from his own government, Walker and a band of misfits must stop him, before all races in the galaxy are exterminated. Walker is unaware, however, that the key to their survival lies deeply rooted in his own history's past.