A book published Monday sheds some new light on the mysterious man at the centre of the so-called Airbus Affair.

The book details the complex financial dealings of Karl-Heinz Schreiber, the Canadian-German businessman accused of paying secret commissions in a series of big international business deals. Schreiber's alleged secret payments remain the subject of a multi-year investigation by the RCMP, and Schreiber himself remains in Canada fighting an extradition request from Germany.

While the book, written by investigative journalists Stevie Cameron and Harvey Cashore reveals much about Schreiber's secret money trail, some of the most crucial questions still remain unanswered.

Karl-Heinz Schreiber

It was of course the RCMP's early attempt to learn more about Schreiber, and that infamous letter to Switzerland for his banking records, that prompted former prime minister Brian Mulroney to sue the federal government. A suit which in turn prompted Ottawa to give Mulroney an apology.

But for many years now, Schreiber's role as a middleman in international business deals, including the sale of Airbus jets to Air Canada, has provoked one overarching question. Where did the millions of dollars in secret commissions Schreiber received eventually wind up?

The Last Amigo, written by journalist Cameron and CBC the 5th estate producer Cashore, is essentially an exercise in forensic accounting, painstakingly tracing the money trail, at least as far as it can go for now.

The book portrays Schreiber as a schmoozy bon vivant with ready and easy access to Ottawa's top power brokers through the Mulroney years. It documents the payment of commissions to Schreiber on the Airbus deal, along with several others, and the movement and disbursement of those millions of dollars to various Swiss bank accounts.

From there the money trail leads to a number of high profile lobbyists and lawyers in Ottawa.

In Germany, it's now known some of Schreiber's commissions wound up in the hands of German politicians, eventually touching off one of the worst political scandals in that country's history. What's still not known is whether any Canadian politicians received similar payments.

Cameron told CBC's As It Happens there's still no evidence of that, only cryptic references in Schreiber's various diaries. "His diaries are full of them. But the problem is ... that he notes all the people he's giving money to in his day timers, but we have to have proof of those payments."

There is, for example, the famous 'Britan' account, which some have suggested may have been codenamed for Brian Mulroney. Mulroney emphatically denies knowing about any Swiss bank account, or of ever having received a penny from Schreiber, and there is no evidence to the contrary.

But there's still the fact the 'Britan' account existed and that more than $500,000 Canadian passed through it. But Cashore concedes the money trail dies after that.

"A month after he set up the account, you have a cash withdrawal out of that account of $100,000, and then a further $100,000. And where that money wound up, only Karl-Heinz Schreiber knows right now," said Cashore.

The answers may come in time. RCMP investigators have been poring over Schreiber's bank records for a year now and their investigation continues.

Schreiber, meanwhile, is fighting extradition to Germany where he's charged with fraud. For the moment he is refusing to tell investigators anything about the Canadian recipients of his secret payments.

He does give the book's authors a tantalizing quote though saying, "I could create the most horrible Watergate here in Canada when I want to. But I'm keeping my bullets for the opportune time."