  We study the existence and uniqueness of solutions of $\partial_tu-\Delta
u+u^q=0$ ($q>1$) in $\Omega\times (0,\infty)$ where $\Omega\subset\mathbb R^N$
is a domain with a compact boundary, subject to the conditions $u=f\geq 0$ on
$\partial\Omega\times (0,\infty)$ and the initial condition $\lim_{t\to
0}u(x,t)=\infty$. By means of Brezis' theory of maximal monotone operators in
Hilbert spaces, we construct a minimal solution when $f=0$, whatever is the
regularity of the boundary of the domain. When $\partial\Omega$ satisfies the
parabolic Wiener criterion and $f$ is continuous, we construct a maximal
solution and prove that it is the unique solution which blows-up at $t=0$.
