Overview of the April 2-5, 2001, event. From top to bottom are shown: the 3He++/4He++ ratio in the energy-per-mass ranges 50-150 keV/amu and 150-300 keV/amu; the 3He/4He and 4He+/4He++ ratios, and the fluxes of all He ions as well as He (total) in the energy range 50-150 keV/amu; and the magnetic field strength from ACE/MAG. The interplanetary shock (IP S) is marked by the dashed line. In addition we show the spectra of 4He+, 4He++ and 3He++ before, during and after the shock passage.