Thunderbolt looks very much like an attempt to repeat the highly successful formula of Underworld. But where the earlier film had a triangle situation as three-dimensional as a pyramid based in the curious sort of love affair between the brutish Bull Weed and the gentle, courteously ironic Rolls-Royce …, Thunderbolt operates from a much simpler, more Hollywooden premise which leaves no place for the ambivalent moralities of Sternberg's world…. Clearly conscious of [a] shallowness in the characterisation, Sternberg tries to compensate by elaborating a cat (the mysterious lure of the underworld) and a dog (tranquil domesticity) as symbols of the emotional dilemma: a symbolism which eventually identifies Thunderbolt with the dog (dumb devotion), and would have been more effective, as well as more in keeping with twilight Sternbergian ethics, had Ritzy the cat been allowed to retain a hint of feline equivocation. Although it looks terrific, shot with all Sternberg's usual loving care for half-lights and shadows, this first half of the film seems to catch him in an uneasy attempt to reduce his vision to a 'reality' commensurate with the simplified characterisation. The visit to the Black Cat Club, for instance, never quite takes off into the dream-like fantasy of the gangster's ball in Underworld, despite its striking visual play with the predominantly Negro staff and customers against the glittering silvery-white decor, because Sternberg is evidently forcing himself to impose a note of vulgarity in order to contrast unfavourably with the later (and sadly mawkish) scenes of domestic bliss in the Moran home…. Sternberg's intermittent earlier experiments with sound … come into their own [in the scene of the wedding ceremony in the jail]: a single set, purely imaginative in quality, which allows the rivals to glare at each other from their cages set opposite each other across a narrow passageway (with the bars making caressing patterns of menace); allows for adjoining cells so that the voices-off of other prisoners add contrapuntally to the silent dialogue between the two men staring at each other (a fine moment when another prisoner asks Thunderbolt to describe the new inmate he cannot see, and Thunderbolt launches into a scathing pen portrait of a seducer); and above all, allows for the musical commentary, also mostly off, first by a prisoner singing spirituals, then by a harmony quartet, and finally by a prison concert orchestra, which traces the progress of the emotional duel being played out. With this rigid formalism, Sternberg recaptures his emotional exactness (i.e. ambivalence)…. Thunderbolt may be minor Sternberg, but no Sternberg film is less than essential viewing. (pp. 187-88)

Tom Milne, "Retrospective: 'Thunderbolt'," in Monthly Film Bulletin (copyright © The British Film Institute, 1974), Vol. 41, No. 487, August, 1974, pp. 187-88.