I think "Peter" was a german guy (or came from Switzerland/Austria/Lichtenstein) who was a spy (for Ireland, not for Germany...a traitor, "rat"). His address in Vienna was fake. Well-dressed, can pay an expensive hotel, gold teeth...he had money. He was very ill, methastatic prostate cancer, half kidney, many heart attacks, but didn't use any pain killers in his big pain (sometimes just stand on the street, without moving...I think that was the hardest minutes when he had terrible pains, agony what poor guy covered with cigarette smoking). He shuffled the proofs out of sight and committed suicide. I agree with the director use quickly resorbed poison to die what led to heart attack (no wtarer in the lung, cause of death isn't drowning!). And he had many heart attack earlier too, the medical examiner don't recognize that this led to his death, a poison indicated heart attack, very tricky. I think his parents died earlier, no sisters or brothers, no wife, no kids, no living relatives...just colleagues who can remain silent, won't risk their lifes. The guy was a great spy material, "rat", traitor for Ireland. There is a military basis too, not only beautiful seaside! Who was "Peter"? Maybe remain unsolved forever, similar as Isdal Woman or "Jennifer Fergate" , both women in Norway. Big chance that Isdal Woman was also a military spy (secret rocket tests at that place in 1970, Norway) like "Peter Bergmann" and her accent sounded also german. https://en.wikipedia.org/wiki/Peter_Bergmann_case Directed by Ciaran Cassidy.