When a plot to assassinate the President comes to light, Garrison is implicated and goes on the run to clear his name - and save the day. Among the Secret Service agents on his trail are old friend and rival Kiefer Sutherland and hot young Latina rookie Eva Longoria. Oh, and, Garrison is having an affair with the First Lady.
The film, which Douglas also produced, is preposterous, but moves along at a brisk pace, with some engaging set pieces. It's especially pleasing to see Douglas back in the big-budget thriller format at which he is so expert.
"I liked the idea of doing something in detail about the Secret Service and what goes on behind the doors," he says. "The thing about those agents is that they have to defend that guy. I was intrigued by how you train yourself to put your body in front of somebody else and take the bullet."
Although The Sentinel is not due out in the UK until September, it is released this month in the US, only three weeks after Basic Instinct 2, the disastrous sequel to the 1992 smash in which Douglas was paired with Sharon Stone. What does he think of it?
"I haven't seen it, so I'm off the hook," he smiles. "I gather it's got bad reviews. I am reminded, however, that the first film was good and that's a hard thing to try to recreate. Sharon was great but it's interesting that we went to Kim Basinger originally for that role. She had done Nine and a Half Weeks, so she wasn't quite ready for Basic Instinct."
As well as casting Basinger in The Sentinel, it's refreshing to see Douglas, as producer, employing TV stars such as Sutherland (now best known for 24), and Longoria (making a definitive leap to the big screen from Desperate Housewives). It's often forgotten that Douglas himself made his name as a TV actor in a long-running cop series, and struggled to make the leap to the big screen.
"In those days, there weren't many people who could make the transition from television," he says. "Back then, people thought if they could get you for free, why pay to see you in the theatre?"
Douglas was born in 1944, the son of Kirk Douglas and his Bermudan actress wife, Diana Dill but his parents divorced when he was six and he went to live with his mother and her new husband. For years, Michael had an uneasy relationship with his father and struggled to be something other than Kirk's son".
After a few minor film roles, Michael's real success, modest compared with that of his father, was as Karl Malden's sidekick on the first three years of ABC's 1972 hit TV series The Streets of San Fancisco.
The punishing shooting schedule of the series eventually made him feel at ease on screen. "I had terrible stage fright, but they couldn't kick me off the show," he laughs.
A sideways move into producing, initially on One Flew Over the Cuckoo's Nest in 1975, enabled him to cast himself in meatier big-screen roles, starting with The China Syndrome in 1979, then - after an earlier three-year career break necessitated by a serious ski-ing accident in 1980 - in Romancing the Stone in 1984 and its 1985 sequel, Jewel of the Nile.
When, in 1987, he won an Oscar for Wall Street and topped the box office with Fatal Attraction, he felt he was "stepping out of the shadow of my father and gaining my own sense of identity". But after playing flawed characters in provocative blockbusters Basic Instinct and Disclosure, it began to seem as if his life was imitating his art.
He was treated for alcohol abuse then, allegedly, for sex addiction, and in 2000 was divorced by his first wife, Diandra, who ended their 23-year marriage, citing his philandering and the fact he wasn't a "proper father" to their son, Cameron.
Douglas's first-born is now 27; he was charged with possession of cocaine in 1999 (later dropped) and father and son seem to have replayed the dynamic Michael had with Kirk.
Today Douglas jokes about his old reputation, placing all his addictions in the past. There has, alongside his new wife and family, been another linchpin in his life in the past few years.
His liberal political views found a focus when he was appointed a messenger of peace for the United Nations, with a special interest on disarmament, by UN Secretary General Kofi Annan in 1998, though, he insists, "My philanthropic work comes after family - and before career."
His dedication to his family perhaps explains his fierce protection of his personal life. In 2003, of course, he and Zeta-Jones sued celebrity magazine Hello! for publishing unauthorised wedding photographs since its rival, OK!, had paid £1 million for exclusive rights to the pictures.
Douglas made it clear at the time that the principle was everything - which is fortunate, because though they won damages of £14,500 for invasion of privacy, they also had to pay hefty legal costs.
Indeed, as his vocal Left-leaning political views attest, Douglas doesn't suffer corruption, injustice or fools. "As I grow older, I want to behave to somebody else as I would want them to behave to me. I don't like bullies and I see them in this little entertainment world all the time."
He says he is stricter with the children than Zeta-Jones. "She spoils them when she comes back from working," he says. "I'm the disciplinarian. Her mom's the worst, though. She arrives with three suitcases and goes home with one because she doles out the toys."
Douglas and the two children have just had a brief holiday in New York, visiting Zeta-Jones while she is filming. "We took them to the Planetarium. Took them to Beauty and the Beast on Broadway and to see Ice Age 2. They went ice skating in the park. It was exciting. Dylan is just the sweetest little guy but he's a handful. Carys is so cute and very feminine."
If Douglas is beginning to take on more work himself - he has a small role as Kate Hudson's father in this summer's You, Me and Dupree and is about to play a manic-depressive eccentric in the offbeat comedy The King of California - he has no desire to return to the demanding obligations of a major movie star. Nor does he wish to attempt any action sequences that might cause him embarrassment.
"I don't profess to be anything other than what I am," he says frankly. "In The Sentinel, I started to deal with hamstring pulls and all of that, so I am looking for more professorial roles.
"Particularly when you have a younger bride, you've got to be careful that you recognise the realities of how old you are and that you are not pretending to be anything other than that."
