  We study the bispectrum in the Effective Field Theory of Large Scale
Structure, consistently accounting for the effects of short-scale dynamics. We
begin by proving that, as long as the theory is perturbative, it can be
formulated to arbitrary order using only operators that are local in time. We
then derive all the new operators required to cancel the UV-divergences and
obtain a physically meaningful prediction for the one-loop bispectrum. In
addition to new, subleading stochastic noises and the viscosity term needed for
the one-loop power spectrum, we find three new effective operators. The three
new parameters can be constrained by comparing with N-body simulations. The
best fit is precisely what is suggested by the structure of UV-divergences,
hence justifying a formula for the EFTofLSS bispectrum whose only fitting
parameter is already fixed by the power spectrum. This result predicts the
bispectrum of N-body simulations up to $k \approx 0.22\, h\, \text{Mpc}^{-1}$
at $z=0$, an improvement by nearly a factor of two as compared to one-loop
standard perturbation theory.
