The last of three appearances in the series by Richard Leech, the others being E17, Mr. George (1960) and E21 The Collector (1960).
The last of three appearances in the series by John Cairney, the others being E28, Ascent to Murder (1960) and E36 Cargo of Death (1960).
The second of two appearances in the series by Elisabeth Wilson, the first being in E26, The Girl with Grey Hair (1960).