An exactly soluble model describing a spin
S=1 antiferromagnetic chain doped with mobile
S=1/2 carriers is constructed. In its continuum limit the undoped state is described by three gapless Majorana fermions composing the
SU(2) triplet. Doping adds a scalar charge field and a singlet Majorana fermion with different velocity. We argue that this mode survives when the Haldane gap is added.