Sherlock Holmes S01 E05 The Red-Headed League

Jabez Wilson, a London pawnbroker, comes to consult Sherlock Holmes and Doctor Watson. While studying this prospective client, both Holmes and Watson notice his red hair. Wilson tells them that some weeks before, his young assistant Vincent Spaulding urged him to respond to a newspaper advertisement by "The Red-Headed League" offering highly-paid work to only red-headed male applicants.