Those who sipped or sniffed ether and chloroform in the 19th century experienced a range of effects from these repurposed anaesthetics, including preternatural mental clarity, psychological hauntings, and slippages of space and time. Mike Jay explores how the powerful solvents shaped the writings of Guy de Maupassant and Jean Lorrain — psychonauts who opened the door to an invisible dimension of mind and suffered Promethean consequences.