The second film with William, The Lone Wolf Strikes (1940), was given to Salkow, who did well enough to be given the next three. The Lone Wolf Strikes had a screenplay by Dalton Trumbo (later to become one of the Hollywood Ten who refused to testify before the Un- American Activities Committee) and featured Joan Perry, the wife of studio head Harry Cohn, as the female lead. It set what was to become a standard formula for the films, with the Lone Wolf helping an innocent party (usually an attractive female) solve a crime while he himself is suspected by the police because of his former life. (When shown in revival or television seasons, the formula can seem tiresome, but in their day they were of course seen months apart.)

Eric Blore, as a former pickpocket turned valet, was a cast regular and provided a neat contrast to William. The Lone Wolf Meets a Lady (1940) was one of the best of the series, with Jean Muir the damsel in distress and Salkow keeping up a lively pace. The Lone Wolf Takes a Chance (1941), involving the theft of a set of engraving plates, was almost as good, but Salkow's last film in the series, The Lone Wolf Keeps a Date (1941) was less memorable, lacking pace and featuring a poorer supporting cast than average.

Salkow moved on to a lively musical starring Ann Miller, Time Out for Rhythm (1941). One of the first musicals set against a television background, its thin plot about rival theatrical agents was bolstered by Miller's splendid tap-dancing and a cast that included Rudy Vallee, the Three Stooges and Glen Gray's Casa Loma Band, who featured in the most striking sequence when the musicians disappear into a black background so that only their instruments are seen.