Spring is in the air

Glancing out of the window next to my colleague's desk I saw two young things smooching on the wall below our office. When I pointed this out to her, she was dismissive: "All kinds of things go on by that wall! The year before last I saw a man behaving very oddly, poking about in the bushes behind the wall. I called the police and they arrested him: he'd hidden a gun behind that wall!"