In the next room, Andrew crouched over Emmanuel's Avid system. He was playing back the final version of a Bach Cantata music video. 

A pretty workaday effort, concert genre. Flashing lights, the crowd on their feet, pulsating close-ups of the tenor Frank Kelley.

"He's like an angel" Donna said, involuntarily reaching to the screen to touch Frank's tousled hair. 

Then, just as Frank Kelley and Jayne West were making their way through crowd to the limo, the screen went dark. The shooting footage came up as Mary pushed Andrew aside.

Soon Mary had a little palette of frames from John's post-shooting dance, transformed into simple lines. Like a cheerleader, he'd been forming the letters S and K, repeatedly.

"Amazing," Kush said.

"Pretty simple, really" Andrew chuckled. "Image Processing 101. Deblurring. Edge Detection. Morphology. Add a little region-of-interest processing, and you're all set."

"Not much to go on, though: S and K."