  Neutral Kaon mixing plays an important role in the phenomenology of the
standard model and its extensions because of its sensitivity to high-energy
scales. In particular epsilon_K, parameterising indirect CP violation in the
neutral Kaon system, serves as an important constraint on models of new physics
and is well suited for the indirect search for heavy new particles. In order to
exploit this potential, a precise prediction of the standard-model background
is crucial. I give a short summary of the standard-model prediction of
epsilon_K, and present our recent NNLO QCD calculation of the charm-quark
contribution eta_cc to the |Delta S| = 2 effective Hamiltonian. We find a large
36% shift with respect to the NLO value that leads to eta_cc = 1.87(76),
shifting the standard-model prediction to |epsilon_K| = 1.81(28) x 10^-3.
