The Green Man by Kingsley Amis

Like all good coaching inns, The Green Man is said to boast a resident ghost: Dr Thomas Underhill, a notorious seventeenth-century practitioner of black arts and sexual deviancy. However, the landlord, Maurice Allington, is the sole witness to the renaissance of the malevolent Underhill. Led by an anxious desire to vindicate his sanity, Allington strives to uncover the key to Underhill’s satanic powers. All while the skeletons in Allington’s own cupboard rattle to get out.