In 1648, during the English Civil War, Captain Sylvester switches sides between the Parliamentary and Royalist camps as his interests dictate, while King Charles I is on the run from Oliver Cromwell's troops.
This historical adventure is set during the English Civil War. When King Charles I is captured by Roundhead forces led by the tyrant Colonel Judd and his right-hand man Captain Sylvester, it is up to a band of locals loyal to the King to try and rescue him. They are helped by Judd's daughter Claire who secretly helps them in defiance of her father.—Anonymous
England, 1648. Edward Beverley [Jack Hedley], aka The Scarlet Blade, a Royalist supporter of King Charles I, rushes to collect the king from his father's mansion ahead of a group of Roundheads lead by Colonel Judd [Lionel Jeffries] and Captain Sylvester [Oliver Reed]. Edward's father [John Stuart] stays behind while Edward and his siblings Philip [Clifford Elkin] and Constance [Suzan Farmer] escape with the king. When Judd arrives at the mansion he threatens Beverley with execution, but he refuses to say where the king has gone, sealing his own fate.
In the woods, King Charles I [Robert Rietty] thanks Edward for his assistance, unknown they are being spied upon by a villager. The Roundheads offer a reward for information leading to the capture of the king so the villager tells Judd what he has seen. However, Judd tricks the villager and puts him in jail to protect him from Royalist villagers who would be angry at him receiving his reward publicly.
Judd's daughter Claire [Jane Thorburn] arrives at the mansion. She doesn't share her father's anti-Royalist views. Judd's men capture King Charles and bring him back to the mansion. Judd orders the king be taken to Hampton Court and his accomplices executed.
That night Claire spies Beverley's former servant Jacob [Harold Goldblatt] opening a secret door in one of the rooms of the mansion so that he can leave the grounds secretly via an underground passage. Jacob goes to where Edward is hiding. Along with Edward's accomplices Gonzales [Leslie Glazer] and the gypsy Pablo [Michael Ripper], they vow to attack the Roundheads wherever and whenever they can in revenge. In return for their attacks, the Roundheads randomly select villagers for execution.
Sylvester attempts to court Claire but she resists his approaches. Sylvester mentions he has seen Claire conversing with Major John Drury [Charles Houston], a Royalist, and threatens to tell Judd unless she agrees to him spending time with her. She has no choice but to agree. While they are dining with Judd and his officers, Edward throws a rock with a message through the window vowing a death for every murder. Despite Judd's men's efforts, Edward escapes from the grounds.
Claire informs Sylvester about Jacob and the secret door. Sylvester therefore believes Jacob is working with Edward so tells Judd of his plan to execute Jacob in the woods at the gallows tree, on the basis that Edward will show up to rescue him and he and Judd can capture Edward.
Sylvester questions Jacob about Edward's whereabouts, saying it is the only way he can save Jacob and Edward. Jacob is convinced of Sylvester's intentions and reveals Edward's hiding place. Sylvester goes there and explains to Edward that he has decided to help them in order to win the hand of Claire.
Next day Edward and his men overpower the Roundhead soldiers lying in ambush at the gallows tree. When the execution party arrives, they attack and successfully rescue Jacob. They all return to Edward's hiding place where they plan to rescue the king and also a group of Royalist refugees.
Judd realises information about the ambush must have been leaked from within and inadvertently places Sylvester in charge of investigating who the traitor is.
Edward and Claire and the other Royalists successfully rescue the refugees. Claire has fallen in love with Edward so she resists Sylvester's advances when she returns to the mansion. In retaliation, he threatens to reveal her true beliefs to her father.
Major Bell [Duncan Lamont] arrives to deputise for Judd while Judd is away undertaking other orders. Bell is suspicious of Sylvester's activities and the recent attacks that have taken place. Bell is keen to capture Edward while Judd is away and instructs Sylvester to capture Edward's sister Constance and hold her captive to draw Edward out.
Claire reveals to Sylvester that the king is to be moved from Hampton Court to The Tower of London in three days so they start to make plans for his rescue.
A search by a Roundhead soldier finds Edward's hiding place but Edward overpowers him. However, other Roundheads find Constance in the woods and capture her. Edward, Philip and Pablo are suspicious that Sylvester has betrayed them as only he would have known where they were hiding.
Edward sneaks into the mansion via the secret passage and door and overpowers the guards in order to rescue his sister. However, during their escape Edward is captured while his sister rides free.
Claire pleads with Sylvester to stop Edward's execution the next day. When he does not comply, she realises he has betrayed them. In the grounds she meets Major Drury who enters the mansion to try and kill Sylvester but Sylvester gets the better of him instead.
Philip, Constance, Claire, and Pablo discuss rescuing Edward and the king. Although they are keen to attempt the rescues, Philip knows it is very risky and many lives would be lost if they go ahead.
Next day Edward is brought into the village square to be hanged. As the noose is put around his neck, Judd returns and stops the execution. He wants Edward interrogated for information about his accomplices and the plot to rescue the king. Bell informs Judd that there was no need to stop the execution because he already knows Sylvester is Edward's accomplice inside the Roundheads. Judd arrests Sylvester but Sylvester reveals Judd's daughter Claire is also an accomplice of Edward so if he is to be brought to trial, then so will Claire which would be embarrassing for Judd. Judd draws his pistol and shoots Sylvester dead, telling his men Sylvester was shot resisting arrest. Judd asks Claire if the accusations are true. She confirms they are but concedes the king is doomed because they will be unable to rescue him now.
In his cell, Edward has refused to talk. Judd goes down to the cell to shoot him but Edward overpowers him and the guard and escapes on horseback with Claire's help.
Philip and the other Royalists attempt to attack the Roundheads. Edward and Claire arrive during the battle and see Philip killed and the Royalists defeated. Edward and Claire are forced to hide with Pablo's gypsies at their encampment. Judd and his men pass by and stop. Although Judd recognises Claire and Edward, he just advises the gypsies to stay in the woods and then rides off.
