The Five Thatchers

Ammo: Corruption of “Amo"- “Love.

Spoilers ahead for “The Five Thatchers"

Amo, or, Love, was the secret weapon, the “ammo" that AGRA hoped to use against Mycroft Holmes' colleague, “Love”. AGRA had information incriminating her deeply in various crimes, which would likely have ended in her dethroning and imprisonment for various crimes against the Crown, likely including high treason. When AGRA revealed its knowledge, Love conspired with terrorists to have them killed. Unfortunately, Rosamund “Mary" Morstan, AG"R"A, and one of her AGRA buddies survived, neither of them knowing what their two AGRA buddies knew, so unable to tear down “Love". HOWEver, Sherlock deduced her identity and her secrets, and exposed her in front of Mary, John, and possibly Mycroft (This is all from memory, so forgive my possible errors, this episode required two viewings from me to understand and this was several months ago, but the general plot I know). When Sherlock belittled her, she snapped and tried to kill him, but Mary took the bullet, dying instead. This set the catalyst for Euros to pose as a therapist and set in motion the Final Problem. As you can see, this makes The Five Thatchers, (based on the Six Napoleons and the AGRA treasure) the single most instrumental episode in the series to setting the finale in motion.