How I work

[rebbonk]

I sat in the van keeping the house under surveillance. It had been about two hours when the woman finally left. I hunched down and watched her in the rear view mirror until she turned the corner, then I ran to the wall and vaulted it. I fell to the ground and lay silently listening to see if I had been noticed. Then slowly I crawled along on my chest until I reached the door. I looked around to ensure that I was unseen.

Then, slowly, deliberately, I carefully opened the letterbox and posted it. Then I ran back to the van without looking back and drove off at great speed.

Spoiler:

And another 'Sorry you weren't home' card is successfully delivered.