In 1501, a city in Italy has been taken by a coup d'état while its rightful ruler, Arnolfini (Fernando Hilbeck), is away. Arnolfini promises some mercenaries 24 hours of looting if they succeed in retaking the city, and they do so. But in their revelry, Arnolfini decides that he wants them gone. Hawkwood (Jack Thompson), the commander of the troops, is caring for a young nun he mistakenly attacked during the siege. Arnolfini promises to get medical attention for her and Hawkwood leads Arnolfini's cavalry, betraying his former lieutenant, Martin (Rutger Hauer). The cavalry ejects the mercenaries from the city without their loot. Soon after, Martin's son is stillborn. Burying the infant unearths a wooden statue of Saint Martin of Tours – a saint with a sword. The mercenaries' cardinal views this as a sign from God to follow Martin as their new leader.
Arnolfini's son, Steven (Tom Burlinson), is betrothed to Agnes (Jennifer Jason Leigh). They meet for the first time and eat from a mandrake to magically fall in love, then the entourage is attacked and robbed by Martin's band. Arnolfini is seriously injured, and Agnes is hauled away, concealed among her valuable dowry. Martin discovers Agnes later evening as they strip the caravan of valuables. The men desire to gang rape her but Martin decides to take her himself. He rapes Agnes while she at first taunts him and then begins to flirt with him, hoping to gain Martin's protection.
The mercenaries come upon a castle where, unknown to the mercenaries, the inhabitants are infected with the Plague. They capture the castle easily with the help of Agnes. She induces Martin to fall in love with her and works on the other mercenaries to accept her. She appears to have given up on her former life. Meanwhile, Steven is determined to rescue her and turns to Hawkwood. Hawkwood only wants to live a quiet life, married to the former nun he had injured. Steven, becoming as ruthless as his father, seizes the nun to force Hawkwood to help his pursuit of Martin. They locate Martin and the mercenaries. They do not have sufficient force to take the castle and lay siege to it. In the castle, Martin asks Agnes where her true loyalty lies; she is noncommittal, hinting that the winner takes all. Outside, the Plague spreads among Steven's forces and infects Hawkwood.
Steven builds a siege tower to storm the castle, and Martin destroys it with something Steven had tried earlier: gunpowder. Steven's soldiers are killed as Steven scales the tower's ladders, and he falls into the castle grounds. The mercenaries capture Steven and shackle him in the courtyard. Agnes pretends to join in the abuse of the captive Steven and even makes love to Martin in his presence. Using a new medical technique Steven had learned (cutting the black sores on the infected body), Hawkwood cures his plague. He cannot continue the siege alone but, before leaving for additional troops, he catapults pieces of an infected dog into the castle. One chunk lands near the chained Steven, who flings it into the castle's water well. Agnes sees this and Steven tells her that she can decide whether to tell the mercenaries.
The mercenaries wish to leave the castle, fearing the Plague, but Martin persuades them to stay. At the next meal, Agnes watches as they drink infected water. As Martin begins to drink, she slaps the cup from his hand. Many mercenaries soon show signs of the Plague sickness and hurl Martin into the well. As she did after Steven's capture, Agnes pretends to join in the abuse of Martin. Hawkwood and Arnolfini have recovered from their wounds and return with an army. Inside the castle, Steven needs Martin's key to escape from the shackles, and Martin needs Steven to get out of the well. The two cooperate, but upon seeing the besieging army, Martin flees to the belfry. Steven frees himself and, as the battle rages, races to find Agnes. During the fighting, the belfry catches fire. Before long, all the mercenaries but Martin are dead.
Martin confronts Agnes. She claims that she loves him, but he prepares to murder her rather than allow her to return to Steven. As Martin is strangling Agnes, Steven attacks. Martin, a cunning and hardened mercenary, overpowers Steven. He almost drowns him when Agnes strikes Martin on the head, and she and Steven flee the blazing castle and reunite with Hawkwood. As Agnes and Steven embrace, Agnes sees Martin over Steven's shoulder, escaping from the castle, a sack of loot on his shoulder. She says nothing.
After tiring of attempting to have his controversial Dutch films subsidized by the government, Verhoeven looked elsewhere for funding for Flesh and Blood, eventually securing most of the budget from Hollywood studio Orion Pictures. However, Orion soon requested changes, feeling that the film needed a love interest; thus, instead of focusing on the relationship between Hawkwood and Martin, Agnes was introduced and attention turned to her romantic entanglement with both Martin and Steven. Verhoeven later said: "The triangular relationship [of] Martin–Agnes–Steven is now the main story line, but in retrospect I think we should have stuck with Hawkwood and Martin. The failure of Flesh+Blood was a lesson for me: never again compromise on the main story line of a script."
In addition to a cast featuring American, Australian, British and Dutch actors, attempting to handle an international co-production funded by multiple sources who all wanted to take the film in different directions overwhelmed Verhoeven, who had also not storyboarded the film in a bid to achieve a "looser visual approach". There were a number of delays and disagreements because of the subsequent improvisational style of filming; many members of the cast and crew also arrived and left when they pleased to party on a local beach. One of the most notable disagreements was between Verhoeven and Hauer, who wanted to cultivate a reputation for playing heroic characters rather than villains, as he did in Ridley Scott's Blade Runner (1982). This was at odds with Verhoeven's intent to portray the moral ambiguity of its characters and the Middle Ages as a "stinking time in which to live" to distance it from typical medieval fantasy depictions of the period. This caused a bitter rift to develop between the two, who have not worked together since.
Some of the film was censored, including the rape sequence. This upset Jennifer Jason Leigh who was opposed to censorship. "It's a hard scene to watch," she said. "Brutal and ugly as rape is, I know it's going to upset a lot of people. But the film is extraordinary. Paul Verhoeven is so gifted."
Though the film received worldwide release in the summer of 1985 in the United States, Orion Pictures gave the film a limited theatrical release on August 16, 1985, in Los Angeles and New York City. Thus, the film did not gross a large amount in the country, and by most accounts, performed poorly. By 1986, the film was showing in the U.S. on HBO, a business partner of Orion Pictures.
Verhoeven has hypothesized on the reasons for the film's failure at the American box office in the years since its release, including statements that it was "too cynical and downbeat" to be a hit. Professor of film and literature at California Polytechnic State University Douglas Keesey suggested that the film had "no hero to root for and no happy fantasy element to lighten its unpleasantly realistic depiction of the Middle Ages".
The film's financial failure caused Verhoeven to move to the United States in September 1985 in order to better understand American culture and what films would be suited to its audience. In addition to this, his previous films, notably Spetters (1980), had been protested by members of the Dutch public and it had become difficult to gain financing to shoot productions in his home country.
It was shot in Spain, in Belmonte, Cuenca, Cáceres and Ávila.
Although unsuccessful at the box office upon release, the film has become a critical and cult favorite. It maintains a 79% approval rating on the review aggregator Rotten Tomatoes based on 14 reviews.
The movie inspired Berserk creator Kentaro Miura, as he said it himself in a 2003 interview when he won the Tezuka Osamu Cultural Prize (2002), he specially based the design of Guts in the character Martin as portrayed by actor Rutger Hauer.