The Bella Coola suffix "-m" has been analyzed in the literature as two or even three separate morphemes, based on the variable effects it has on the transitivity of its base. The segment is argued for here as a single morpheme with a unified meaning, specifically as a marker of a special case of one definition of the middle voice, referred to as the "non-unitariness" of event-participants. The cross-linguistically unusual "transitivizing" uses of "-m" are shown to fall out from the presence of a second, individual entity in a semantically typical middle clause, independent of the application of the middle-marker itself. Contains 17 references. (Author/MSE)