  We report on the observation of a rare neutrino event detected by Baikal-GVD
in April 2021. The event GVD210418CA is the highest-energy cascade observed by
Baikal-GVD so far from the direction below the horizon. The estimated cascade
energy is $224\pm75$~TeV. The evaluated signalness parameter of GVD210418CA is
97.1\% using an assumption of the E$^{-2.46}$ spectrum of astrophysical
neutrinos. The arrival direction of GVD210418CA is near the position of the
well-known radio blazar TXS~0506+056, with the angular distance being within a
90\% directional uncertainty region of the Baikal-GVD measurement. The event
was followed by a radio flare observed by the RATAN-600 radio telescope,
further strengthening the case for the neutrino-blazar association.
