Friedmann Holtzer is a field agent working in Interpol’s Hamburg office. He is sent to interview Remus Carey and return the transcript of his interview to Aurelie Paget at Interpol headquarters in Lyon.
The first time we encounter him is in book 2, Blowfish, where Remus Carey says,
I can see why they chose you, Holtzer. You’re anonymous: a perfect blend of everything that won’t stand out in a crowd. That’s a compliment, by the way. I don’t think I could aspire to be so forgettable. It seems a waster that they’ve put you in friendly terrain. They could pitch you east as a faceless ex-pat; teach you the basics to set you up. Nothing too deep – just eyes and ears where needed… Perhaps a little further than that. A former Soviet state?