Lester Del Rey 
Pursuit 

Fear cut through the unconscious mind of Wilbur Hawkes. With almost physical violence, it tightened his throat and knifed at his heart. It darted into his numbed brain, screaming at him. He was a soft egg in a vast globe of elastic gelatine. Two creatures swam menacingly through the resisting globe toward him. The gelatine fought against them, but they came on. One was near, and made a mystic pass. He screamed at it, and the gelatine grew stronger, throwing them back and away. Suddenly, the creatures drew back. A door opened, and they were gone. But he couldn’t let them go. If they escaped….