“Earnshaw was desperate. Montgomery fired him on the spot and told him he was going to the authorities to report the embezzlement. He swore Earnshaw would be in prison by nightfall. Earnshaw stormed out of the mill, went up the street to a receiver’s shop, and purchased a muff gun. When he returned to the mill, he couldn’t sneak into Mr. Montgomery’s office because Mr. Coombe was in the warehouse, the mill workers were in the mill proper, and two workers were cleaning up a flour spill in the passage immediately outside Montgomery’s office door. They were creating a cloud of flour dust as they shoveled up the spill. Earnshaw went outside, around the back of the mill, and accessed the walkway over the waterwheel, which also passed by Montgomery’s open office window. He leaned in and shot Montgomery in the head.”

“But the explosion …” Juliette trailed off.

“According to the scientist I consulted, flour dust is more explosive than gunpowder under the right circumstances. It’s possible either the striking of one of the shovels against stone in the passageway produced a spark, or the firing of the pistol in that small room set off the explosion. Though the door to the hallway was closed, a transom window over the door was open, letting in enough of the flour dust to ignite when the pistol went off. The blast sent Mr. Earnshaw backward, hard into the railing on the walkway, and stunned him for a time.

“When I found Earnshaw, he was dangerously near to dropping into the water. When questioned, however, he was quick enough to say he had been on the walkway trying to see if Mr. Montgomery was in his office, since they had an appointment that morning and the way was blocked by the men cleaning up the spill. He acted as if he had not yet seen Mr. Montgomery that day.”

“What about the anarchist who was killed in the mill later?” Sir Bertrand asked. “Was Earnshaw involved, or are we looking for another killer?”

“The anarchist was an expert in explosives, and we believe he had been sent by Jasper Finch’s group to lay the plans for destroying the mill once all the repairs were completed. It was his misfortune to have chosen the very night Earnshaw had sneaked in to look for the murder weapon. The explosion jerked the gun from his hand as he held it through the window, and he was certain it was in the office somewhere. He killed Pietro Todisco with a blow to the head and managed to find the gun not in the office but wedged into a crack between the rail on the walkway and the mill wall.”

“Two murders, two mill workers killed, another wounded so badly he later died, and for what?” Juliette asked. “To hide a theft.”