Satan's Incubator by Randolph Craig

JEFFREY FAIRCHILD'S sedan, at first glance, seemed as dissimilar from Dr. Skull's old jalopy as night is from day. But under their hoods, they were identical; the only two of their kind in use in New York. Like the jalopy, the bright new sedan was equipped with a powerful Diesel motor which Jeffrey had designed and installed himself. And also like the jalopy, its smooth painted sides were of heavy plated steel.

It was a little after one in the afternoon when Jeffrey headed toward Queens. He was tired and bruised and his eyes had to strain to see anything at all--but he didn't realize his weariness. There was a tiny package wrapped in cotton-wool, and sewed into the lining of his hip pocket. It was a small package, but there were few men who would have risked carrying it, even insulated as it was against jolting.