A woman's wild story about killers from space leads two Chicago detectives into a bizarre case in this mystery by the Edgar Award-winning author.   Ed and Ambrose Hunter, nephew and uncle, have partnered up to open their own detective agency in early 1950s Chicago. With their experience solving the case of Ed's father's murder, among others, they have the skills to take criminals down. And as carnies, they've encountered all sorts of unusual characters.   But it's still a surprise when a woman asks them to protect her from the Martians who are supposedly targeting her. It's an easy story to scoff at, but when she actually turns up dead soon afterward, Ed and Am are resolved to find out who on Earth is responsible . . .   "[Ed and Am are] an engaging pair of detectives." --The New York Times