The constriction came from an arm around his neck, but he couldn't see to whom it belonged, and there was no place to move aside in the corner of the egg.
The enemy tried to choke him. 
mnli hypothesis: The enemy tried to choke him.  premise: The constriction came from an arm around his neck, but he couldn't see to whom it belonged, and there was no place to move aside in the corner of the egg.