Complex sentence: If Tanner has scared the associate then he takes a local gangster called Cosy to a chopper taking him out of town, or if he has taken the explosives across town then Tanner aids a group of gangsters left in the lurch in Chinatown.
Split into simpler sentences: If Tanner has scared the associate, then he takes a local gangster called Cosy to a chopper taking him out of town. Alternatively, if he has taken the explosives across town, Tanner aids a group of gangsters left in the lurch in Chinatown.