  We re-examine a closed-string model defined by altering the boundary
conditions for one handedness of two-dimensional propagators in
otherwise-standard string theory. We evaluate the amplitudes using
Kawai-Lewellen-Tye factorization into open-string amplitudes. The only
modification to standard string theory is effectively that the spacetime
Minkowski metric changes overall sign in one open-string factor. This cancels
all but a finite number of states: As found in earlier approaches, with enough
supersymmetry (e.g., type II) the tree amplitudes reproduce those of the
massless truncation of ordinary string theory. However, we now find for the
other cases that additional fields, formerly thought to be auxiliary, describe
new spin-2 states at the two adjacent mass levels (tachyonic and tardyonic).
The tachyon is always a ghost, but can be avoided in the heterotic case.
