Single-crystal X-ray diffraction has shown that the high-critical-temperature (T-c) phase of the filamentary molecular superconductor (BEDT-TTF)(2)Ag(CF3)(4)(1,1,2-trichloroethane) [BEDT-TTF = bis(ethylenedithio)tetrathiafulvalene] contains layers of BEDT-TTF radical cations with alternating kappa- and alpha'-type packing motifs. This molecule-based superconductor with dual BEDT-TTF packing motifs has a T-c five times higher than that of its polymorph that contains only kappa-type packing.