I am very familiar with the salon, I have been there numerous times (and probably won't go back ever again). There are two entrances into the salon, one in the front, which is right on one of the busiest streets in Wenatchee. You can also pull behind the house and there is a small parking lot (maybe 6 parking spots) and a back door you can walk in through. I do not recall seeing an entrance to the basement back there, but then again, I never particularly looked for one.
If my thinking is correct, the only entrance to the basement is IN the salon. See this review that someone wrote about salon couture in June of this year:
http://local.yahoo.com/info-45215035-salon-couture-wenatchee
"...the shampoo area is rundown and the basement door is always open exposing a dirty staircase..."
If the only entrance is in the salon, I HIGHLY doubt he could get Mackenzie in the salon without anyone seeing them.
The salon is usually fairly busy, not as loud and as busy as you'd expect a salon to be. They play music, not loudly, and of course there are the occasional hair dyers running. My intuition is that the murder did not occur at the salon... I don't think it is consistently busy/loud enough for Wilson to feel (... if he feels anything at all....) comfortable murdering someone downstairs within earshot of the salon. If Mackenzie was able to fight back at all, a few hits on the wall or a scream could have very well been plenty to get others to hear her.
But if she wasn't killed at the salon, I'm not sure where it could have been done. My only thought is that the murder occurred, he "stashed" or hid her body somewhere for a few hours while he dumped her car, recovered the body somehow, and carried it downstairs to his basement where he proceeded to do whatever with it. The blood on the wall could just be from an attempt to dismember or whatever he did after she was dead. :sick: Disgusting.