London, December 2019. Two young boys, Habib and Loz, are trying their luck at selling knock-off pain remedies to pensioners. But they are troubled by an encounter with a potential elderly customer and a young man with a blood-smeared face. Mumtaz Hakim wants to help if she and her partner Lee Arnold can, even though there's no way their detective agency could reasonably charge the boys. While they set about uncovering the truth behind the odd situation in the shadow of St Paul's Cathedral, they find themselves drawn into a gruesome investigation involving an old man and a newborn baby.