  We show that three open questions in particle physics and cosmology: the
origin of neutrino mass, the identity of dark matter, and the origin of the
baryon asymmetry of the universe can be explained simultaneously in the
three-loop seesaw model proposed by Krauss, Nasri, and Trodden. We discuss the
difficulty of successful leptogenesis with three right-handed neutrinos, and we
propose a scenario with four right-handed neutrinos that satisfies all
observational constraints. This scenario predicts a sleptonlike particle as
light as a few hundreds GeV that can be probed by future collider experiments.
