Lachlan Werner is a talented ventriloquist with strong character acting skills who is lumbering with a thin script filled by simplistic humour. The conceit of a satanic ritual, led by his witch puppet and ending in unexpected chaos, allows him to fall back on crowd interactions, which deliver predictable laughs. There is some play with the physical limitations of a puppet, and much mockery of Werner’s own slight physicality, but the pacing and balance between comedy and the ritual itself is uneven.

Werner’s mock innocence (he begins dressed as a choirboy) and his subsequent transformation into a demon provides the most effective comedy. Although his voice-throwing ability is very impressive, the relationship between puppet-master and marionette is overly familiar: the witch is aggressive and dominant, Werner is the victim. Appropriately for a late-night show, the jokes become coarser and rowdier throughout the hour, after a long period of scene-setting and developing both characters.

Pitched somewhere between a queer cabaret aesthetic and a traditional light entertainment ventriloquist routine, Voices Of Evil demonstrates Werner’s potential without closing on the humour. It ends with Werner in full sexual predator mode (a threat he turns on himself) but the production never launches into the anarchic mayhem it seems to promise.

Lachlan Werner: Voices Of Evil, Pleasance Courtyard, until 27 August, 10.30pm.