This is the third episode at the site:
Plenty of episodes there, just scroll down … in this episode, Templar is to meet the daughter of his friend at an al fresco cafe table by the river … he’s called away by a faux call … the rest follows. Not sure but the villain sounds as if it’s an Englishman pretending to be Australian*.
* Maurice Colbourne (1939-1989) was the villain, born in Sheffield, died at 49. Kidnapped girl was Cathryn Harrison (London 1959-2018), died at 59. Girl gondolier was Carole André, no relation to Annette (Paris 1953, still alive), the Saint (Woking 1943, still alive). Episode was in 1978.