  We report on an investigation into stellar evolution and nucleosynthesis in
the low and extremely low metallicity regime, including models of stars with a
pure Big Bang composition (i.e. Z=0). The metallicity range of the extremely
metal poor (EMP) models we have calculated is -6.5 < [Fe/H] < -3.0, whilst our
models are in the mass range 0.85 < M < 3.0 Msun. Many of the EMP and Z=0
models experience violent evolutionary episodes not seen at higher
metallicities. We refer to these events as `Dual Flashes' since they are
characterised by peaks in the hydrogen and helium burning luminosities
occurring at roughly the same time. Some of the material processed by these
events is later dredged up by the convective envelope, causing signifcant
surface pollution. These events have been reported by previous studies, so our
results reaffirm their occurrence -- at least in 1D stellar models. The novelty
of this study is that we have calculated the entire evolution of the Z=0 and
EMP models, from the ZAMS to the end of the TPAGB, including detailed
nucleosynthesis. We have also calculated the nucleosynthetic yields, which will
soon be available in electronic format. Although subject to many uncertainties
these are, as far as we are aware, the only yields available in this mass and
metallicity range. In this paper we briefy describe some of the results in the
context of abundance observations of EMP halo stars. This work formed part of
SWC's PhD thesis (completed in March 2007) and a series of subsequent papers
will describe the results of the study in more detail.
