  We introduce the chain geometry $\Sigma(K,R)$ over a ring $R$ with a
distinguished subfield $K$, thus extending the usual concept where $R$ has to
be an algebra over $K$. A chain is uniquely determined by three of its points,
if, and only if, the multiplicative group of $K$ is normal in the group of
units of $R$. This condition is not equivalent to $R$ being a $K$-algebra. The
chains through a fixed point fall into compatibility classes which allow to
describe the residue at a point in terms of a family of affine spaces with a
common set of points.
