America at Large: On August 19th I was at the Peristeri Boxing Hall in Athens when the mobile phone rang. The sports editor back in Boston informed me a Massachusetts lad named Tyler Hamilton had just won a gold medal in the cycling time trial and that Team Herald was being scrambled into red-alert mode.

Now, I'm such a cycling buff that until that moment I never realised medals were even awarded for this particular discipline. I'd assumed a "time trial" was just what the name would imply, which is to say, a trial for some nebulous, but more important, event. Fortunately Steve Harris, the other half of Team Herald, was in closer proximity to the venue and was able to track down Hamilton.

And it had all the makings of a feel-good Olympic story if ever there was one. Hamilton, who'd raced in the shadow of Lance Armstrong for the past several years, had upon crossing the finish line half-deliriously called for his wife, Haven, to be brought to his side.

That day Hamilton recalled the tribulations that had brought him to the summit of Mount Olympus. He had been an accomplished skier who had won a college scholarship in that sport, and had taken up cycling only 10 years ago as part of his rehabilitative process after being injured in a downhill accident while skiing for the University of Colorado. He had finished fourth in the 2003 Tour de France despite racing most of the way with a fractured clavicle.

He had been doing well in last July's race before a crash in the Pyrenees and a resultant back injury forced him out of the Tour.

And in a truly heart-rending moment, Hamilton brandished his talisman - a memento of his deceased dog Tugboat, who had expired during the Tour de France.

"A lot of people might think 'Oh, he's just a dog', but for me it was just as hard as losing a family member," said a tearful Hamilton, displaying Tugboat's collar, which he had worn about his neck during his gold-medal ride. "He brought me luck."

At some point in this post-race celebration Hamilton was also pulled aside and asked to pee in a bottle. Two days ago the result was made public, and the 33-year-old American cyclist is likely to become the fourth Athens gold medallist to be stripped of his Olympic championship.

Joining the chorus of 24 other athletes banned during the Athens Games, Hamilton immediately proclaimed his innocence.

"I worked hard for that gold medal, and it isn't going anywhere," he said at a press conference hastily convened in Switzerland by Phonak, the cycling team with which he had signed on as captain before this year's Tour de France.

"Anyone who knows me knows that is completely impossible," said Hamilton. "I can tell you what I did and did not put into my body. Cycling is very important to me, but not that important. If I ever had to do that, I'd hang the bike on the rack."

Tracked down at the Marblehead family home by Boston newspapers, Hamilton's father Bill offered his own penetrating analysis of the drug-test results. "This," proclaimed Hamilton pere, "is just bullshit."

"I have always been an honest person. I am devastated to be here tonight. My family is devastated. My team is devastated. My friends are devastated," said Hamilton in Switzerland on Tuesday. He added he would "fight this until I don't have a euro left in my pocket".

The banned substance detected in Hamilton's post-race test (confirmed by a second test administered two weeks ago in Spain) turns out not to be a designer steroid or human growth hormone, but blood.

Somebody else's.

The procedure is apparently the latest twist on the "blood-doping" technique perfected by Scandinavian distance runners in the 1970s. Banned by the IOC since 1980, that process was used to boost an athlete's performance by increasing the ratio of oxygen-producing red cells in his system, but in its classic form, the athlete was at least doped with his own blood.

Whose did Tyler get? Lance Armstrong's? Tugboat's? Just before the Athens Games, the IOC had authorised sophisticated tests which would reveal a whole host of previously undetectable transgressions, including designer steroids, human growth hormones, as well as a synthetic hemoglobin called erythropoietin. The new DNA-based procedure, developed in Australia, can also identify blood transfusions.

Hamilton's sample revealed a mixed red blood cell population, indicating a transfusion. Under Olympic guidelines, this in itself would constitute a failed test.

Dick Pound, the president of the World Anti-Doping Agency, who seems to regard each failed test as a personal triumph, said on Tuesday if Hamilton's test remains positive, "then it will be the first-ever case of this form of doping being detected".

Back home in Marblehead, Bill Hamilton described his son's apprehension as "a witch hunt". "They've tried to bring down Lance Armstrong for years," said the cyclist's father. "And now they're trying to bring down Tyler."

Yeah. And the dog ate my homework.