Run about the hallway. No stairs allowed

It was morning and the kids had just been set free for another day of playing and exploration.  Thorn had bounded out the door, full of life and ready for ways to expend it.  Glancing behind him he spotted Taly also coming out, “hey, Tal, wait a moment.” Thorn bounded in front of his sister to make sure there was no way for her to miss his calling for her.  “Hey, that last race was fun.  Let's do another?”

Thorn waved a paw ahead of them, “We can use the stairs like a starting line.  We run a lap all away around this floor.  Whoever gets back to the stairs first wins!”  It sure seemed a great idea to Thorn.  He knew his sister wasn’t much for fights unless she had changed her mind, but she seemed to have enjoyed their last race together.  “Uh, but if you run down the stairs you lose.” Was there any better way to learn why not to run down the stairs than to fall down them the very first day he saw them?

"Carpathius Family"