A Federal agent (Johnny Mack Brown) goes undercover to discover who is stealing payroll money from trains. Myron Healey. Janet: Lois Hall. Williams: Tommy Farrell. Mae: Christine McIntyre. Directed by Lewis Collins., As was customary in his late Monogram westerns, Johnny Mack Brown plays an undercover agent in Colorado Ambush. Brown is sent to Colorado to stem the activities of a particularly vicious outlaw gang. The leader of the gang is played by Myron Healey, who also wrote the script. The best sequence involves Healey and saloon gal Christine McIntyre; it’s the standard “We’re neither one of us any good,” dialogue exchange, but it’s played with depth and finesse. Myron Healey also wrote and co-starred in the subsequent Johnny Mack Brown oater Texas Lawman (1951).