  Our goal is to study the supermembrane on an $AdS_4 \times \cal M_7$
background, where $\cal M_7$ is a 7--dimensional Einstein manifold with $N$
Killing spinors. This is a direct way to derive the $Osp(N|4)$ singleton field
theory with all the additional properties inherited from the geometry of the
internal manifold. As a first example we consider the maximally supersymmetric
$Osp(8|4)$ singleton corresponding to the choice $\cal M_7 = S^7$. We find the
explicit form of the action of the membrane coupled to this background geometry
and show its invariance under non--linearly realised superconformal
transformations. To do this we introduce a supergroup generalisation of the
solvable Lie algebra parametrisation of non--compact coset spaces. We also
derive the action of quantum fluctuations around the classical configuration,
showing that this is precisely the singleton action. We find that the singleton
is simply realised as a free field theory living on flat Minkowski space.
