Tunnel

A very hidden tunnel entrance and exit.

In the tunnel, you can use the rear observation port to see if the slider is successfully pulled up(when B disappear).

Spoiler: Hints

Tunnel entrance is in the house.
Using Claustrophobia to the observation port.

Spoiler: Video

Found the first bit straight away due to chance. Not sure what actually happened to open things up for the finish and looking at the video i am still not sure. Was impressive though.

In the end everything visible is a big red herring Buff,really hidden...but I did it without hints Thabks for sharing @935

This is very disappointing. After all the time tapping everywhere, I resorted to the VS. Getting B into the tunnel requires too many tries and when he's triggering the magic, it fails every time. Not close enuff to the access. Moving on.