  We discuss a model for the lepton sector based on the seesaw mechanism and on
a $D_4$ family symmetry. The model predicts the mixing angle $\theta_{13}$ to
vanish. The solar mixing angle $\theta_{12}$ is free--it will in general be
large if one does not invoke finetuning. The model has an enlarged scalar
sector with three Higgs doublets, together with two real scalar gauge singlets
$\chi_i$ ($ i = 1, 2$) which have vacuum expectation values < \chi_i >_0$ at
the seesaw scale. The atmospheric mixing angle $\theta_{23}$ is given by $\tan
\theta_{23} = <\chi_2>_0$ /<\chi_1>_0$, and it is maximal if the Lagrangian is
$D_4$-invariant; but $D_4$ may be broken softly, by a term of dimension two in
the scalar potential, and then < \chi_2_0$ becomes different from < \chi_1_0$.
Thus, the strength of the soft $D_4$ breaking controls the deviation of
$\theta_{23}$ from $\pi / 4$. The model predicts a normal neutrino mass
spectrum ($m_3 > m_2 > m_1$) and allows successful leptogenesis if $m_1 \sim 4
\times 10^{-3} \mathrm{eV}$; these properties of the model are independent of
the presence and strength of the soft $D_4$ breaking.
