Let There Be Light — R. Cooper

In war-torn Europe of 1872, Karol and Hart devoted themselves to protecting England and the peace England maintained. Hart was a spy and bodyguard for Karol, a brilliant but hotheaded scientist. Their partnership was almost unstoppable... until Hart could no longer bear to see Karol in dangeror with other menand seeing Hart repeatedly put his life on the line came to terrify Karol. Then a horrible accident separated them for what they believed would be forever.