In the shadow of St Paul's, Arnold and Hakim are drawn into an investigation involving an old man and a newborn baby. 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. While they set about uncovering the truth, they find themselves drawn into a gruesome investigation involving an old man and a newborn baby.