A new mechanism for the photodeactivation of electronically excited norbornadiene in the gas phase is investigated by high-level ab initio quantum-chemical calculations. Ivana Antol on page 1439 presents potential energy surfaces of low-lying singlet excited states of norbornadiene. Deactivation from the valence V1 to the ground state goes through an Olivucci–Robb-type conical intersection that adopts a rhombic distorted geometry. The deactivation path has negligible barriers, thereby making ultrafast radiationless decay to the ground state possible. The cover image illustrates a norbornadiene “avalanche” jumping between different potential energy surfaces toward the ground state minimum.