  We present the high resolution spectroscopic study of five -3.9<=[Fe/H]<=-2.5
stars in the Local Group dwarf spheroidal, Sculptor, thereby doubling the
number of stars with comparable observations in this metallicity range. We
carry out a detailed analysis of the chemical abundances of alpha, iron peak,
light and heavy elements, and draw comparisons with the Milky Way halo and the
ultra faint dwarf stellar populations. We show that the bulk of the Sculptor
metal-poor stars follows the same trends in abundance ratios versus metallicity
as the Milky Way stars. This suggests similar early conditions of star
formation and a high degree of homogeneity of the interstellar medium. We find
an outlier to this main regime, which seems to miss the products of the most
massive of the TypeII supernovae. In addition to its value to help refining
galaxy formation models, this star provides clues to the production of cobalt
and zinc. Two of our sample stars have low odd-to-even barium isotope abundance
ratios, suggestive of a fair proportion of s-process; we discuss the
implication for the nucleosynthetic origin of the neutron capture elements.
