Episode Description: Beware, spoilers! To read - hover over the text.
Double murder. Two people are not connected to each other. One mathematician, the other just a thief. Bright intuition helps Sherlock to find a unique mathematical formula for a bright clean wall. Formulas are visible only under ultraviolet light. This formula is hunted by many. But it turned out that this murder was committed by a woman, although she seemingly had an alibi, but Joan figured out her trick, survivor and the witness confirmed it.