Watson, the seed of a case is barely visible in this London fog. Observe closely before drawing conclusions.
Watson, one does not build a theory without data. Secure your premises before taking a single step.
Watson, even I require Lestrade's official authority occasionally. Find a reliable partner to clear this impasse.
Chasing a suspect into the dark alleys without a lantern is folly, Watson. Halt before you lose your way.
Watson, send a telegram to those who possess the missing information. Collaboration is the logical path forward.
Watson, a flickering gaslamp requires steady fuel, not a sudden deluge. Dispense your resources with calculated precision.
Watson, when the trail goes cold and the carriage is stuck, abandon the pursuit. Obsession clouds logical deduction.