  We present Virgil, a MIRI extremely red object (MERO) detected with the
F1000W filter as part of the MIRI Deep Imaging Survey (MIDIS) observations of
the Hubble Ultra Deep Field (HUDF). Virgil is a Lyman-$\alpha$ emitter (LAE) at
$z_{spec} = 6.6312\pm 0.0019$ (from VLT/MUSE) with a rest-frame UV-to-optical
spectral energy distribution (SED) typical of LAEs at similar redshifts.
However, MIRI observations reveal an unexpected extremely red color at
rest-frame near-infrared wavelengths, $\rm F444W - F1000W = 2.33 \pm 0.06$.
Such steep rise in the near-infrared, completely missed without MIRI imaging,
is poorly reproduced by models including only stellar populations and hints
towards the presence of an Active Galactic Nucleus (AGN). Interestingly, the
overall SED shape of Virgil resembles that of the recently discovered
population of Little Red Dots (LRDs) but does not meet their compactness
criterion: at rest-frame UV-optical wavelengths Virgil's morphology follows a
2D-S\'ersic profile with average index $n = 0.93^{+0.85}_{-0.31}$ and $r_e =
0.43$~pkpc. Only at MIRI wavelengths Virgil is unresolved due to the coarser
PSF. We also estimate a bolometric luminosity $L_{\rm bol} = (8.4-11.1)\times
10^{44}\rm~erg~s^{-1}$ and a supermassive black hole mass $M_{\rm BH} =
(4-7)\times 10^7\rm ~ M_\odot$ in agreement with recently reported values for
LRDs. This discovery demonstrates the crucial importance of deep MIRI surveys
to find AGN amongst high-$z$ galaxies that otherwise would be completely missed
and raises the question of how common Virgil-like objects could be in the early
Universe.
