  We discuss a mechanism of neutrinoless double beta decay, where neutrinos of
different flavours come into play. This is realized by effective
flavour-violating scalar interactions. As one consequence, we find that within
the normal mass ordering the neutrino effective mass may no longer vanish due
to contributions from other flavours. We evaluate the necessary nuclear matrix
elements, consider the interference between the standard diagram and the new
scalar one, and analyze a UV-complete model that realizes the scalar
interaction. Tests of the complete model are possible at colliders and future
neutrino experiments. Our scenario represents an alternative mechanism for
neutrinoless double beta decay, where nevertheless lepton number violation
resides only in Majorana mass terms of light neutrinos.
