Helios 1 observed a magnetic cloud on the spacecraft's closest approach to the Sun (0.3 AU) on March 26, 1976. Fluxes of energetic particles detected by the spacecraft generally decrease during the passage of a cloud, but in this case the smooth intensity depression was interrupted by a sharp peak-like increase coinciding with a deep drop of the magnetic field magnitude. This behavior is observed for protons and electrons in several energy bands. A possible explanation of this event is given by the spheroidal model of magnetic clouds, applicable for the plasmoid geometry (having field lines fully disconnected with the Sun). ¿ American Geophysical Union 1995