We have analyzed energetic protons in the energy range 30 to 500 keV and energetic electrons ≥75 keV obtained with the Max-Planck-Institut/University of Maryland sensor system on ISEE-1 during a plasma sheet crossing on March 26, 1978. The behavior of protons with energies of more than ~100 keV is very different from that of the ~30 to ~100 keV protons which represent the suprathermal tail of the plasma sheet distribution. The more energetic ions appear on a time scale of serveral minutes following a northward turning of the tail magnetic field. At about the same time the plassma measurements show a velocity of ~200 km/s in the tailward direction. This velocity enhancement is first seen at ISEE-1 and later on at ISEE-2, which is earthward of ISEE-1. The temporal sequence of the energetic particle, magnetic field, and plasma observations and the proton and electron anisotropies are discussed in terms of acceleration near a magnetic neutral line which occurs well within the plasma sheet. In this framework the magnetic neutral line would move earthward, followed by a magnetic island. The extent of the neutral line would be limited to the dusk side of the tail. No disruption of the plasma sheet is observed as compared to large-scale substorm activity.