Adventure Comics #378

Adventure Comics #378 (On Sale: January 28, 1969) has a Legion of Super-Heroes cover by Neal Adams.

"Twelve Hours to Live" is by Jim Shooter, Winslow Mortimer and Jack Abel. At a celebration of Brainiac 5's birthday, five Legionnaires are poisoned. Brainiac 5 analyzes the poison and determines that it will kill each of them in twelve hours. Brainiac 5 uses the time to find a cure. Superboy returns to the 20th century and attempts to stay busy. Duo Damsel returns home to visit her parents for the last time. Karate Kid tracks down the Fatal Five on a suicide mission. Projectra mopes around the city until she meets Myron Marks, who lifts her spirits.

As the twelve hour period comes to an end, the poisoned Legionnaires return to headquarters. Brainiac 5 admits that he could not find an antidote. The Legionnaires then compose a will, before each succumbs to the effects of the poison. Brainiac 5 makes one last effort to save them using the Miracle Machine, but he runs out of time. When all the Legionnaires fall unconscious, their killer gloats over his victory. Reprinted in Legion of Super-Heroes Archives Vol. 9 HC.

Edited by Mort Weisinger.