Ever think about how the mayfly man could be a metaphor for Mary… The mayfly man (Mary) adopts the facade of a perfect man (woman), starts dating Tessa (John) and seems perfect for her (him), they “instantly connect” and the mayfly man (Mary) seems perfect for Tessa (John), but the mayfly man (Mary) is actually secretly a murderer and the only reason he (she) started dating Tessa (John) was to get closer to his (her) target…. Sholto. (Sherlock.)