  We prove the existence and main properties of signed Young modules for the
symmetric group, using only basic facts about symmetric group representations
and the Brou{\'e} correspondence. We then prove new reduction theorems for the
signed $p$-Kostka numbers, defined to be the multiplicities of signed Young
modules as direct summands of signed Young permutation modules. We end by
classifying the indecomposable signed Young permutation modules and determining
their endomorphism algebras.
