Throw them a ball to play with

You find a tennis ball near the edge of the fence. Unsure on how to begin the match, you throw it at the shoeless infected. As if activating a rocket, she jumps into action, hitting the ball with such great, devastating **** to the other side that you hardly see it. The other infected, as if waiting her entire life for the moment, raced to the side to hit it, returning it back at her opponent. And so it went like that a few times, back and forth, until the shoeless infected miscalculated her slide, and missed the ball hitting her side of the court by mere few inches. The ball rolled on, until slowly stopping just short of the fence. When it stopped, the two infected went back to "normal".

You can't help but stand there breathless, shocked at the turn of events. Even by living standards that was amazing! Whoever these two were, they must've been so dedicated to tennis that they still played with such fervour.

You pick up another ball, and throw it to the other infected this time. Again, they jumped to action. It's almost scary how fast they are; no matter how much you tried, you'd never reach their kind of speed in your life. This time the shoeless infected won, sending the ball into a sideways arc, landing it on the side where her opponent was not. Again, once the game stopped, they returned to "normal" once more.

You are nearly mesmerised at their ferocity and grace. You must see them play again. And again. And again. You watch for so long several hours pass. By the end, you're unsure who is winning. But even the greatest of games become boring after a while. Still, you appreciate you've found these two.

You throw them one last ball as you leave through the deadbolt gate in the fence, leaving them to their game.