You are tracking a dangerous criminal who has already killed one person at least. You are about to leave your home planning to enter his house. What should you bring with you on this dangerous mission? You can learn a lot from Sherlock Holmes in The Adventure of the Speckled Band:

“And now, Watson, this is too serious for dawdling, especially as the old man is aware that we are interesting ourselves in his affairs; so if you are ready, we shall call a cab and drive to Waterloo. I should be very much obliged if you would slip your revolver into your pocket. An Eley’s No. 2 is an excellent argument with gentlemen who can twist steel pokers into knots. That and a tooth-brush are, I think, all that we need.”