  In recent years, there has been substantial progress in the derivation of
nuclear forces from chiral effective field theory. Accurate two-nucleon forces
(2NF) have been constructed up to next-to-next-to-next-to-leading order (N3LO)
of chiral perturbation theory and applied in microscopic nuclear structure
calculations with a good degree of success. However, chiral three-nucleon
forces (3NF) have been used only at N2LO, improving some miscroscopic
predictions, but leaving also several issues, like the "Ay puzzle'" of
nucleon-deuteron scattering, unresolved. Thus, the 3NF at N3LO is needed for
essentially two reasons: For consistency with the 2NF, and to (hopefully)
improve some critical predictions of nuclear structure and reactions. However,
there are indications that the 3NF at N3LO (in the so-called Delta-less version
of the theory) is rather weak and may not solve any of the outstanding
problems. If this suspicion is confirmed, we have to go beyond, which may be
similar to opening Pandora's Box. In this talk, I will discuss the various
possible scenarios and how to deal with them.
