Solar Warden by Peter Fuller

A ticking time bomb, an enemy that will stop at nothing, untested technology and a spy who targets Solar Warden in a way they never imagined. Earth faces unprecedented dangers and challenges as the reptilians and grays change their tactics and up the ante to a threat level never before experienced. Newly promoted Lieutenant Colonel Richardson harbors a dark secret Scarecrow is intent on discovering. Meanwhile, the Solar Warden team is hoping the detection of a damaged enemy vessel will lead them to the source of recent, lethal attacks. The discovery of alien intel points the humans to a surprise none expected, while the entire Solar Warden team is left reeling at the sudden death of a beloved comrade.