Two For Tanner by Lawrence Block
He is 34 years old and hasn't slept a wink since a piece of shrapnel destroyed the sleep centre in his brain during the Korean War. Evan Tanner loves lost causes and beautiful women. The FBI has a thick file on him; the CIA taps his phone and a super-secret intelligence agency wants him to be their man!
Would you believe Evan Tanner in the guise of a slightly batty, butterfly collector? Trotting through the woods, flailing his net? You would? So did nearly everybody else. Everybody except the gang of guerrilla bandits who decided it was safer and saner to snare Tanner than to let Tanner snare butterflies. They stripped him, stuffed him into a cage and told him: 'Upon the rising of the sun we will lead you to the chopping block and sever your head by driving the blade of an axe through your neck....'