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 'essential oils'. But they are troubled by an encounter with an elderly customer and a young man with a blood-smeared face. When Habib's big sister Iqra hears the boys discussing what happened, she puts them in touch with Lee Arnold and his partner Mumtaz Hakim. While they set about uncovering the truth behind the odd situation, they find themselves at the heart of a gruesome investigation involving the discovery of a newborn's bones.