  We address the dynamics of a single spin embedded in the tunneling barrier
between two superconductors. As a consequence of pair correlations in the
superconducting state, the spin displays a rich and unusual dynamics. To
properly describe the time evolution of the spin we find the generalized
Wess-Zumino-Witten-Novikov term in the effective action for the spin on the
Keldysh contour. The superconducting correlations lead to an effective spin
action which is non-local in time leading to unconventional precessions. Our
predictions might be directly tested for macroscopic spin clusters.
