A series of visits to stricken Asian economies, including Thailand, Malaysia and Indonesia, during the past week by a team of IMF officials was preceded by a visit to those same countries by Mr Summers. His agenda has turned out to be disarmingly straightforward - provide a measure of confidence to markets and investors, and at the same time ensure that governments in the region see the absolute necessity of adopting tough IMF policies as the basis for recovery from the trauma of the past months.
Markets have hung on almost every speech during the trip, and a time graph of the week shows a rapid recovery of confidence in the markets he has visited.
As a result of Mr Summers' long shadow, the closure of Peregrine in Hong Kong, and the jitters there later in the week relating to a large property company, were reduced almost to sideshows in the region.
No one is starting to look for a complete recovery in Asia, but a number of commentators have started to "see a bottom", and one important pundit, Morgan Stanley's Barton Biggs, turned vociferously bullish. The Wall Street Journal at the end of the week even carried an article that saw several fund managers recommending cheap Asian bonds; and a fall of more than 200 points on Wall Street last Friday - which a week earlier could have caused all kind of havoc - failed to diminish a steadying of nerves.
Selective buying in Thailand by international investors also became apparent, and London brokers on Tuesday and Wednesday were reported to be net buyers of Asian equity for the first time in many months.
Unit trust investors are still scarce, possibly due to continued redemption fears, but other London-based fund managers have clearly started to look at the region in a somewhat more positive light.
Mr Summer's trip - to Indonesia, Malaysia, Bangkok, Hong Kong, Peking and Seoul over the space of a week - has done more to stabilise investor confidence than almost anything else since the start of this year.
The Deputy Treasury Secretary has acquired the status of a glorified crusader.
By the close of business on Friday, most Asian markets had already started to shift their focus towards the next stage of the "game" - which has the City looking again at Japan.
Many fund managers were starting to digest the impact of a positive statement by the Japanese authorities that led to a 900-point rise in the Tokyo market on Friday. A positive and buoyant Japan would have a big impact on the rest of the region, and analysts are actively sifting through the tea leaves in order to establish whether this latest move is another false dawn or a real break into a recovery phase.
My day-to-day notes:
Are all my clients lemmings disguised as fund managers?
I went home last Friday thinking that my French contrarian was the only buyer of anything Asian. I get back this morning to find that although HK has collapsed on the news about Peregrine going bust, virtually all my clients want "cheap" offers.
This IMF and US Treasury visit is obviously having an impact. I decide it's time to find out who this bloke Mr Summers really is, and, more importantly, where he is next visiting.
My girlfriend reminds me how lucky I am that I never took a job out in HK last year.
It is no joke, believe me, when hundreds of people start getting axed by the same people that only months ago were shovelling money down their throats. The frightening thing is that it has happened so quickly!
HK makes back most of its loss yesterday, and I am still receiving some buying interest.
This guy Summers is my new hero.
Manila shoots up 95 points today, and Bombay apart (which just had to fall when every thing else is rising!) I can't find any red. The experience of the past six months, however, serves to stop me from going for the bubbly - I think it's better to start my long-delayed savings plan.
My French contrarian wants me to send him a copy of my company's balance sheet.
This is a first. I work for one of the largest banks in the world, and my boss mutters something about "signs of the times". Are we in trouble?
At lunch (orange juice and salad after gym nowadays) I hear questions being asked about the financial viability of two competitors. At least they are not talking about my bank.
Indian stocks again under pressure this afternoon, as US fund managers sell the only market that has held up steadily throughout the last two months.
Japan is up strongly.
I have consistently called this market wrongly this past year, and am therefore reluctant to tell my clients that the Nikkei has turned for real. Our strategist is keen for me to help organise a conference call where we can pass on our view that Japan is turning for real, and that this is good for the rest of Asia. I remind him that this will be the third time in 20 months that we are doing this call. He is not amused.
I find out that Mr Summers is returning to Washington at the weekend. Maybe I should buy some US Treasury stock?
q Gianluca Ricardo is the pseudonym of a City-based financial executive.