The film is loosely based on the Modesty Blaise comic strip created and written by Peter O'Donnell. O'Donnell wrote the scenario for the movie, but the screenplay went through multiple rewrites and the end result differs significantly from the original. Changes range from the relatively trivial, such as hair colour, to a change that horrified the comic strip's fanbase: Platonic Life-Partners Modesty and Willie falling in love and deciding to get married.
The storyline is as follows: Modesty, a secret agent whose hair color, hair style, and mod clothing change at a snap of her fingers, is being used by the British government as a decoy in an effort to thwart a diamond heist. She is being set up by the feds but is wise to the plot and calls in sidekick Willie and a few other friends to outsmart them. Meanwhile, at his island hideaway, Gabriel, the diamond thief, has his own plans for Blaise and Garvin.
O'Donnell wrote a novel based on his version of the screenplay, which (unlike the film) was successful and led to many sequels.
Since the film's release, there have been two additional films produced adapting the comic strip: a 1982 Pilot for a never-produced Americanized series that aired as a TV movie featuring Ann Turkel in the lead role, and in 2004, My Name is Modesty was a low-budgeted production starring Alexandra Staden as a young Modesty prior to her meeting Willie Garvin.
This film provides examples of:
- Adaptation Dye-Job: Modesty is blonde and Willie isn't, the reverse of their hair colours in the comic strip. She does change it to her original colour in a couple of scenes, perhaps as a form of lampshading, and Willie likewise is seen in his normal blonde style early in the film as well before going dark-haired for the rest.
- Arab Oil Sheikh: Abu Tahir, who adopted Modesty as his "son".
- Camp: The high type.
- The Cavalry: The charge at the end done by Abu Tahir and his troops.
- A Glass of Chianti: Gabriel lounges with a glass of blue wine while dispensing his evil orders.
- In Name Only: Zigzagged. Peter O'Donnell famously stated that the film retained only one line from his original screenplay, and his novelization (which kicked off the Modesty Blaise book series) bears little resemblance to the movie beyond characters and certain setpieces.
- Knife Fight: In Amsterdam, both Modesty and Willie end up fighting an opponent with knives at the same time.
- Leaning on the Fourth Wall: This exchange:Gabriel: I am the villain of the piece. I have to condemn you.
Modesty Blaise: But I am the heroine. Don't I get away?
- At one point images of the real-life Modesty Blaise comic strip are shown.
- Protagonist Title
- Psycho for Hire: Mrs. Fothergill. She likes to submit her "minions" to physical exercise and enjoys killing a mime and throwing him off a cliff (it doesn't make much sense in context, anyway).
- Relationship Upgrade: Modesty and Willie. And the action comes to a halt while they do a song and dance number about it.
- Scenery Porn: For fans of architecture, the opening credits that play out over images of classic '60s building lines is as good as Playboy.
- Sissy Villain: Gabriel. So much.
- Volleying Insults: During the period of "truce" between Modesty and Gabriel:Gabriel: Suffragette!
Modesty Blaise: Psychopath!