1970s Western starring Lee van Cleef as an Apache Indian in the Union Army who is charged with investigating the murder of a commissioner. Captain Apache (van Cleef)'s main clue is the riddle buried in the commissioner's enigmatic final words, 'April morning'. The trail leads him into contact with gunrunner Griffin (Stuart Whitman) and an alluring saloon girl (Carroll Baker). However, with suspects and informers dying at an alarming rate, it is clear that the murder was part of a wider plot. Believing he has stumbled upon a major conspiracy, Captain Apache suddenly finds his life at risk as he becomes embroiled in a deadly game of cat and mouse.