the Wallris note

A snippet from chapter 2 of the new novel in progress, Smoke:

The policeman asked Nathan if there was anything else he had noticed about the deceased.
"He handed this to me," said Nathan, "even as he was falling to the ground." It was a folded white paper, with this handwritten message largely scrawled in black ink:

Wallris--
John Bull's ransom will smoke out the black shirts tomorrow. If not, your bridge could burn. Chapman