The first of two appearances in the series by Walter Gotell, the other being in E23, Payment in Advance (1960).
The first of five uncredited appearances in the series by Johnny Rossi, the others being in E9, Dead on Arrival (1959), E18 The Thousand Mile Alibi (1960), E24 Checkmate (1960) and E39 The Absent Assassin (1960).
The first of two uncredited appearances in the series by Michael Beint, the other being in E39 The Absent Assassin (1960).
Oliver Reed makes an uncredited appearance as an Interpol officer in the background while Duval and Mornay are discussing the case. He is also one of the dancers in the Cafe.