  Context. Within $\Lambda$ Cold Dark Matter ($\Lambda$CDM) simulations, Milky
Way-like galaxies accrete some of their satellite galaxies in groups of 3-5
members rather than individually. It was also suggested that this might be the
reason behind the origin of satellite planes. Objects accreted in groups are
expected to share similar specific total energy and angular momentum, and also
identical orbital planes and directions. Aims. Looking at observations of Milky
Way satellites, the dwarf galaxies Leo II, IV, V, Crater II, and the star
cluster Crater 1 were proposed to be a vestige of group infall. The suggested
"Crater-Leo group" shows a coherent distance gradient and all these objects
align along a great circle on the sky. We use proper motion data to investigate
whether the phase-space distribution of the members of the proposed group are
indeed consistent with group infall. Methods. To further investigate this
possibility, we use Gaia Data Release 3 (DR3) and new Hubble Space Telescope
(HST) proper motions, $(\mu_{\alpha*}, \mu_\delta) = (-0.1921 \pm 0.0514,
-0.0686 \pm 0.0523)$ mas yr$^{-1}$ for Leo IV and $(\mu_{\alpha*}, \mu_\delta)
= (0.1186 \pm 0.1943, -0.1183 \pm 0.1704)$ mas yr$^{-1}$ for Leo V, to derive
accurate orbital properties for the proposed group objects. In addition, we
explore other possible members of this putative association. Results. Leo II,
Leo IV, and Crater 1 show orbital properties consistent with those we predict
from assuming group infall. However, our results suggest that Crater II was not
accreted with the rest of the objects. If confirmed with increasingly accurate
proper motions in the future, the Crater-Leo objects appear to constitute the
first identified case of a cosmologically expected, typical group infall event,
as opposed to the highly hierarchical Magellanic Cloud system.
