  The 21cm line emitted by neutral hydrogen (HI) during the Dark Ages carries
imprints of pristine primordial correlations. In models of inflation driven by
a single, canonical scalar field, we show that a phase of ultra-slow-roll can
lead to a null in all the primordial correlations at a specific wavenumber
$k_\textrm{dip}$. We consider scenarios wherein the null in the correlations
occurs over wavenumbers $1 \lesssim k_\textrm{dip} \lesssim
10\,\mathrm{Mpc}^{-1}$, and examine the prospects of detecting such a damping
in the HI signal due to the nulls at the level of power and bi-spectra in
future observational missions.
