Abstract. In finite entropy quantum systems, correlation functions do not decay all the way to zero at late times, but instead hover around a nonzero constant plateau. In the bulk, those same correlation functions evaluated in black hole backgrounds do decay all the way to zero. This apparent tension raises the question of how the bulk gravitational description captures the late time plateau. In this talk I will explain how the plateau can arise in the bulk from a perturbative sum (in the number of wormholes) over wormholes. In particular the amplitude with g wormholes grows as time T to the power 2g+1, and this series over g converges to the plateau. I will discuss three independent derivations of this behavior, within two dimensional dilaton gravity. One is based on random matrices (this is essentially the boundary description). The second is based on Euclidean wormhole amplitudes and cancellations in so-called intersection numbers. The third is based on a purely Lorentzian description of spacetimes with topology change (wormholes). This talk will be based on work in progress with Jorrit Kruthoff and Shunyu Yao, and on a recent paper with the same folks.