The first of three appearances in the series by John Cairney, the others being E36, Cargo of Death (1960) and E38 Pipeline (1960).
The last of three appearances in the series by Julian Sherrier, the others being in E7, Diamond S.O.S. (1959) and E11, The Angola Brights (1959).
The second of two appearances in the series by Howard Marion-Crawford, the first being in E12, The Chinese Mask (1959).