  The presence of cluster-like narrow resonances in the vicinity of
reaction/decay thresholds is a ubiquitous phenomenon with profound
consequences. We argue that the continuum coupling, present in the open quantum
system description of the atomic nucleus, can profoundly impact the nature of
near-threshold states. In this Letter, we discuss the structure of the recently
observed near-threshold resonance in $^{11}$B, whose very existence explains
the puzzling beta-delayed proton emission of the neutron-rich $^{11}$Be.
