Beware the Nice Ones: It's not as if episodes 4 and 6 didn't give us a Ten in the flavor of Oncoming Storm, but those instances were truly nothing compared to this. ...you hurt his Companion badly. You are screwed into the next life.
Bittersweet Ending: Justice is served, but Holmes will have a heck of a time getting to sleep and staying asleep for a long time to come...
Darker and Edgier: Up 'til now, Holmes and Watson have been getting into no more trouble than Martha did in the original season. This marks the first time one of the Holmesian Companions gets in deep.
Late-Arrival Spoiler: The human-Time Lord-Dalek stallholder, whom the Doctor, Holmes, and Watson are delighted to meet. In the twenty-fifth century. Sec's children survived and thrived.
Mythology Gag: Towards "The Reichenbach Fall", most noticeably a little girl seeing Sherlock Holmes and screaming.
Serial Escalation: Though the Cerebus Syndrome doesn't kick in until "Dynamics of a Point", this is the episode that starts racking up the intensity.
Would Hurt a Child: The assassin who killed the ambassador was meant to kill little Noya and does hold her hostage.
