Postmarked the Stars

This is the 4th of 7 Solar Queen Novels. They carried their deadly cargo to the very limits of the universe. The first shock is the body - the dead man aboard the Solar Queen bears a terrifying resemblance to the cargo master, Dane Thorson. Then Thorson and his crew discover the secret behind their strange cargo: an incredible mutation that threatens the universe with an uncontrollable new life form.