  Theory of fast binary chemical reaction, ${\cal A}+{\cal B}\to{\cal C}$, in a
statistically stationary chaotic flow at large Schmidt number ${Sc}$ and large
Damk\"ohler number ${Da}$ is developed. For stoichiometric condition we
identify subsequent stages of the chemical reaction. The first stage
corresponds to the exponential decay, $\propto\exp(-\lambda t)$ (where
$\lambda$ is the Lyapunov exponent of the flow), of the chemicals in the bulk
part of the flow. The second and the third stages are related to the chemicals
remaining in the boundary region. During the second stage the amounts of ${\cal
A}$ and ${\cal B}$ decay $\propto 1/\sqrt{t}$, whereas the decay law during the
third stage is exponential, $\propto\exp(-\gamma t)$, where
$\gamma\sim\lambda/\sqrt{Sc}$.
