I am the Kat that Walks By Itself

Okay, so I've just watched the CSI two-parter "Grave Danger" on DVD. (Whoa!)

A while back I remember coming across a post-"Grave Danger" fic somewhere, possibly on my flist or recced on it, which was a Buffy crossover, a correspondence between Nick and Buffy. But I mustn't have saved it, I can't find it, and I didn't bookmark it and I don't know where I saw it, and Google isn't helping me.

Does anyone recognise the description? Can anyone point to the fic?

Today at lunchtime, I was walking back to work, and I saw a dead sparrow on a windowsill, its wings shut, its claws clenched together, a pathetic sight.

Which gave me a CSI germ of an idea, which I beg folks on my flist who write CSI (okay, so maybe there's only one of you -- are you listening, izhilzha?) to write.

Title: The Fall of Sparrows
Dialogue: "What I want to know," said Grissom, "is what killed the sparrow."