  We study the massless flows described by the staircase model introduced by
Al.B. Zamolodchikov through the analytic continuation of the sinh-Gordon
S-matrix, focusing on the renormalisation group flow from the tricritical to
the critical Ising model. We show that the properly defined roaming limits of
certain sinh-Gordon form factors are identical to the form factors of the order
and disorder operators for the massless flow. As a by-product, we also
construct form factors for a semi-local field in the sinh-Gordon model, which
can be associated with the twist field in the ultraviolet limiting free
massless bosonic theory.
