"Don't you think you have slightly too much chloride in that mixture, Mr. Holmes?"
Basil's thin voice suddenly broke the silence.
Holmes yelped, his hands jerking, and liquid sloshed over the side of the beaker. I hid my face, and its wide grin, in the newspaper as Holmes set down the equipment, turned off the burner, and turned his not-in-the-least amused gaze at the pert mouse sitting atop his table.
"You needn't act as if it were a personal affront, Mr. Holmes, I merely didn't want you to cause an explosion like you did a few weeks ago," he said mischievously, curiously peering into Holmes's microscope.
I hastily stopped laughing as Holmes sent a murderous glare at me before scooting the microscope away from the mouse's inspection.
"You're investigating that Wesson Street bank robbery case, then?"
I dropped my paper in astonishment and Holmes stared incredulously at the mouse, who was regarding him coolly.
"How in the world –"
"Oh, really, Mr. Holmes, it's a very simple deduction – that mud under the microscope has that greenish tinge only found in that area of London. Since there was only one crime committed in that area in the last fortnight of any note, and I doubt you experiment with mud indiscriminately, it is logical to deduce you're on that case for the bank."