This is great fun and a cleverly plotted mystery . Allie Jameson is a neighbour of the Jones’, her parents are in Europe and her aunt is in charge, but she’s a member of a cult that includes new house-guest Ariel. The boys are drawn in when they witness one of the ritual meetings, where the cult invokes the power of Belial, which appears in smoke as a snake and makes a sound that is “singing, but not”. Filled with some great set-pieces - infiltrating the cult’s mansion, breaking and entering the butlers flat and the bombing of a deli - and nice observations - the reasons why people are in the cult and what they want out of it - this is sharply written, with great characterisation and a pace that never flags. Highly recommended.