  Belle II has reported the first evidence for $B^+ \to K^+\nu\bar\nu$ with a
branching ratio $2.7 \sigma$ higher than the standard model expectation. We
explain this, and the MiniBooNE and muon anomalous magnetic moment anomalies in
a model with a dark scalar that couples to a slightly heavier sterile Dirac
neutrino and that communicates with the visible sector via a Higgs portal. We
make predictions for rare kaon and other $B$ meson decays.
