  We study the time-evolution of a quantum particle subjected to time-dependent
zero-range forces in two dimensions. After establishing a conceivable ansatz
for the solution to the Schr\"{o}dinger equation, we prove that the wave packet
time-evolution is completely specified by the solutions of a system of
Volterra-type equations -- the {\it charge equations} -- involving the
coefficients of the singular part of the wave function, thus extending to the
two-dimensional case known results in one and three dimensions.
