  We study the weak decay of the $\Lambda_b$ baryon into $J/\psi\ \phi\
\Lambda$, a process that is particularly well suited to analyze the physics of
some of the recently observed or theoretically predicted exotic hadrons, as one
expects to see their signature in all three final two-body channels. In the
$J/\psi \, \phi$ invariant mass spectrum we study the interplay between the
$X(4140)$ and the $X(4160)$ resonances. The $J/\psi \, \Lambda$ mass spectrum
may help to identify the strange partner of the hidden-charm pentaquark
recently observed by the LHCb collaboration, the existence of which has been
predicted by a chiral unitary approach. We conclude that this strange
pentaquark has a good chance of experimental detection if it is present in the
range between $4450-4500$ MeV. Finally, in the $\phi \, \Lambda$ spectrum we
expect a contribution from a dynamically generated resonance at around $2160$
MeV, but with the present model parameters there is little chance for its
experimental detection.
