  We establish character formulae for representations of the one-parameter
family of simple Lie superalgebras $D(2|1;\zeta)$. We provide a complete
description of the Verma flag multiplicities of the tilting modules and the
projective modules in the BGG category $\mathcal O$ of $D(2|1;\zeta)$-modules
of integral weights, for any complex parameter $\zeta$. The composition factors
of all Verma modules in $\mathcal O$ are then obtained.
