Patrick Martin 
Shifter 
Inversion

Ex-cop William Ryan is dismayed by his corrupt and stagnant society when Villelmus, his doppelgänger from an advanced civilisation from another universe, drops in and makes an offer he cannot refuse: join him in another realm which has evolved to the state William wishes for his own society. But there’s a catch: William must be his doppelgänger’s body double so that Villelmus can continue clandestine rescue missions to other worlds to correct the paths of those worthy civilisations which are headed for catastrophe. 

William struggles with his own ethics when he learns of these missions, but when he is thrust into new worlds his dilemma is shifted from mere contemplation to facing reality. 

Shifter: Inversion, set in a sci-fi backdrop and replete with humour, action, and intrigue is the first in the Shifter series exploring the ethical dilemma of whether it is wise to interfere with the evolution of other societies, and how much a person can change given unusual circumstances.