I'm fully conscious immediately. What on earth was that? I sit up in bed, listening.
Then, a moment later...
It sounds like something large being knocked very slowly down my stairs, a step at a time. Are the cats up to something? I haul myself up, and flick on a light. Stumbling out into the hall, I see Isis sitting at the top of the stairs, looking down intently. Spenser is halfway down the staircase, staring with great concentration at something on the floor. I go down, trying to figure out what's going on. The cats scatter.
There's nothing on the stairs. At least, nothing I can see. Spenser comes back, and crouches himself, a couple of steps above me, staring at the step below him. I stare, too. I can't see anything. Some dust, a smudge of dirt... nothing particularly interesting, at least to me. He's crouched in hunting position, one paw hovering in the air, still as a statue, when suddenly...
He whacks his paw down, hard, on the smudge of dirt.
I stare at the step again, but there's really nothing there. I rub at the little smudge, but Spenser seems unconvinced. So I pick him up and haul him back to bed with me, in an effort to get him settled down.
He does calm down a little and start purring, but he's not in the mood to hang out. So, I let him go, and tuck myself back in. A few moments later... you guessed it...
I waited for the next one, but it never came. I guess he caught... whatever it was.