 Colonel Cato recruits both Erskine and Gunther Haber into the Special Intelligence Unit as civilian operatives due to their intimate knowledge of the South West Pacific and New Guinea.Both are reluctant at first, so Cato fabricates false evidence against them to coerce them into co-operating.Although some episodes were filmed on location in New Guinea, Thailand, Hong Kong, Macau and also in Changi Prison in Singapore, most of the filming was done in the Australian bushland surrounding Sydney.