  Pristine_183.6849+04.8619 (P1836849) is an extremely metal-poor
([Fe/H]$=-3.3\pm0.1$) star on a prograde orbit confined to the Galactic disk.
Such stars are rare and may have their origins in protogalactic fragments that
formed the early Milky Way, in low mass satellites accreted later, or forming
in situ in the Galactic plane. Here we present a chemo-dynamical analysis of
the spectral features between $3700-11000$\r{A} from a high-resolution spectrum
taken during Science Verification of the new Gemini High-resolution Optical
SpecTrograph (GHOST). Spectral features for many chemical elements are analysed
(Mg, Al, Si, Ca, Sc, Ti, Cr, Mn, Fe, Ni), and valuable upper limits are
determined for others (C, Na, Sr, Ba). This main sequence star exhibits several
rare chemical signatures, including (i) extremely low metallicity for a star in
the Galactic disk, (ii) very low abundances of the light $\alpha$-elements (Na,
Mg, Si) compared to other metal-poor stars, and (iii) unusually large
abundances of Cr and Mn, where [Cr, Mn/Fe]$_{\rm NLTE}>+0.5$. A comparison to
theoretical yields from supernova models suggests that two low mass Population
III objects (one 10 M$_\odot$ supernova and one 17 M$_\odot$ hypernova) can
reproduce the abundance pattern well (reduced $\chi^2<1$). When this star is
compared to other extremely metal-poor stars on quasi-circular, prograde planar
orbits, differences in both chemistry and kinematics imply there is little
evidence for a common origin. The unique chemistry of P1836849 is discussed in
terms of the earliest stages in the formation of the Milky Way.
