A crosslinguistically unusual case of morphological fusion, in which two clauses fuse morphologically in the absence of preceding syntactic fusion or clause union, is found in the East Caucasian language Agul. This phenomenon involves a set of “verificative” verbal forms (forms that seek ‘to find out the truth value or the value of an unknown variable’). The verificatives are completely morphologically bound, but manifest clear biclausal properties: in particular, the introduction of a new agentive argument by the verificative (the ergative “verifier”) causes no change in the argument structure of the embedded clause. This article argues that the Agul verificative has grammaticalized from the matrix verb ‘see’ plus an indirect question complement in the conditional form: over time, the two verbal heads have fused into one form. Partial parallels to this development can be found in the related languages Archi and Lezgian, where a semantic shift from ‘see’ to ‘check, find out’ is attested, together with a change in subject encoding from typically experiential (dative) to canonically agentive (ergative). Still, the complete morphologization of the verificative structure in Agul dialects remains exceptional given its comparatively recent origin, the infrequency of the construction, and the general absence of observed cases in which matrix verbs become fused with their complements.