You approach the ghost slowly but even as you take your first steps you hear Filtch's dragged footsteps. You look around for a place to hide but alas, too late. He spots you, grins his manic grin and shakes a finger at you.
'Aye, I did say it was you all along. Mrs Norris will get justice! Stay right here'
I suppose, no point in running now.
Just a minute later McGonagall gasps as she's met with the crime scene.
'Follow me. I think you need to speak to the Headmaster'.