  The two-type Richardson model describes the growth of two competing
infections on $\mathbb{Z}^d$ and the main question is whether both infection
types can simultaneously grow to occupy infinite parts of $\mathbb{Z}^d$. For
bounded initial configurations, this has been thoroughly studied. In this
paper, an unbounded initial configuration consisting of points
$x=(x_1,...,x_d)$ in the hyperplane $\mathcal{H}=\{x\in\mathbb{Z}^d:x_1=0\}$ is
considered. It is shown that, starting from a configuration where all points in
$\mathcal{H} {\mathbf{0}\}$ are type 1 infected and the origin $\mathbf{0}$ is
type 2 infected, there is a positive probability for the type 2 infection to
grow unboundedly if and only if it has a strictly larger intensity than the
type 1 infection. If, instead, the initial type 1 infection is restricted to
the negative $x_1$-axis, it is shown that the type 2 infection at the origin
can also grow unboundedly when the infection types have the same intensity.
