  We study a system of $N_c$ $D3$-branes intersecting $D7$-branes and
$O7$-planes in 1+1-dimensions. We use anomaly cancellation and string dualities
to argue that there must be chiral fermion zero-modes on the $D3$-branes which
are localized near the $O7$-planes. Away from the orientifold limit we verify
this by using index theory as well as explicit construction of the zero-modes.
This system is related to F-theory on K3 and heterotic matrix string theory,
and the heterotic strings are related to Alice string defects in
$\mathcal{N}=4$ Super-Yang-Mills. In the limit of large $N_c$ we find an
$AdS_3$ dual of the heterotic matrix string CFT.
