Parker's climbing went successfully unnoticed because of the distraction Jason and Videl were causing Harrow.

"I am the stain that death leaves! I am --"

Getting drop-kicked in the face, apparently. Jason successfully got his kick in, and before Harrow could recover, Videl managed to clock him in the head with the candlestick. The attacks left him briefly stunned, but he scrambled back on his hands and in a creepy crabwalk, to try to get away, twisting and breaking the limbs of his host to do it.