Months earlier Watson and Holmes put away Lord Blackwood (Mark Strong), an aristocrat who murdered five people via some kind of dark arts ceremony. Watson himself supervised Blackwood's hanging, but when he appears to have risen from the dead, everyone from the police to a secret cabal wants to know how he did it. Blackwood and his legion of followers have plans for world domination via drinking potions and other hocus pocus, while Holmes goes about finding Blackwood in the only way he knows how-- using his "not inconsiderable knowledge" and foolproof logic. Meanwhile, Holmes's old flame Irene Adler (Rachel McAdams) is back in town, a criminal beauty working secretly for a shadowy boss with a penchant for fancy weaponry. Adler pops up from time to time to help Watson and Holmes in their investigations, and it's clear to the audience that she'll throw a wrench in things even when Holmes hasn't quite gotten there.