The Alien Dies at Dawn

The Alien Dies at Dawn by Alexander Blade - Kendall Stone had twelve hours to save a thousand lives. It wasn't much time, especially since someone was making sure he didn't use it!
There was a scream of tortured air over the Mojave Spaceport as a two-man starship dropped on its hot jets toward the wide cement alloy landing field. It slowed and settled gently to the ground. Before the faint wisps of smoke had time to dissipate, the airlock door opened, and a big, broad-shouldered man got out. He dropped lithely to the ground and started off across the field at a quick trot.
He nearly bowled over a field attendant who had been coming toward him.
"Hey!" the surprised attendant said. "Don't you want your ship checked?"
"Don't have time," Kendall Stone called back, as he continued running toward the Customs Office. He glanced at his watch. 1800. Twelve hours till dawn. Twelve hours!
Kendall Stone gritted his teeth and doubled his pace. He was in a super-plus top-level hurry. He'd practically burned a hole in the vacuum between Earth and Mars trying to get to Mojave on time. Twelve hours! At dawn, Galth of Rastol would die in the execution chamber for the crime of murder. And it was up to Kendall Stone to stop it.