  Properties of the depleted Heisenberg spin ladder material series
(C$_7$H$_{10}$N)$_2$Cu$_{1-z}$Zn$_{z}$Br$_4$ have been studied by the
combination of magnetic measurements and neutron spectroscopy. Disorder-induced
degrees of freedom lead to a specific magnetic response, described in terms of
emergent strongly interacting "spin island" objects. The structure and dynamics
of the spin islands is studied by high-resolution inelastic neutron scattering.
This allows to determine their spatial shape and to observe their mutual
interactions, manifested by strong spectral in-gap contributions.
