The Musketeers are given the task of retrieving Comte de Rochefort, the Cardinal's man in Madrid who has escaped from a Spanish prison. They need to work with Rochefort to rescue De Foix before important information falls into the wrong hands.

King Louis demands to experience the life of his carefree subjects, but his night of fun quickly comes to an end when he and d'Artagnan are mistaken for commoners and kidnapped by the notorious criminal Lemaitre to be sold to Spain as slaves. The Musketeers must find and rescue d'Artagnan and the king. Can they save Louis from mortal danger and will they return him to the palace in time for the dauphin's christening? Meanwhile, Rochefort uses the king's absence to become closer to Queen Anne.

When Spanish General Tariq Alaman offers to hand over the formula of a unique and deadlyballoonpowder in exchange for help rescuing his kidnapped daughter, the Musketeers find themselves tangled in a complex web of political trades with the Spanish. Their mission is further complicated when Porthos is captured by Spanish agents. When the Dauphin becomes seriously ill, Constance takes matters into her own hands and risks everything to save his life.

The Musketeers investigate Emilie of Duras, a woman claiming to have visions from God which instruct her to lead her thousands of followers into war with Spain. As word of Emilie's visions trigger unhappy anti-Spanish riots, Aramis is sent to discredit her before she pushes France into an ill-timed war with Spain. Rochefort continues to clash with Spanish Ambassador Perales.

The villagers of Pinon drug Athos and bring him to his ancestral lands in the hopes that he will defend them against an evil baron. Athos refuses, but his fellow Musketeers come looking for him and circumstances soon force him to fight.

Renowned astronomer Marmion gathers the Royal household to his impressive observatory in a transformed old fort to watch a solar eclipse. Rochefort along with The Musketeers escort them but could never have predicted the twist in fate that ensues and the impossible choices that must be made. Who is Marmion really and what is his game? The Musketeers are forced into the fight of their lives with dramatic consequences. Will they accept Milady's help despite their loathing and mistrust of her? It might be their only chance to save the King, Queen and themselves.

The King's cousin is ambushed while under Musketeer escort as she travels from Mantua to Sweden to make a political marriage that will be advantageous to France. The Musketeers must quickly discover who is targeting her to keep both her and the alliance between countries protected. However it emerges that other important figures at Court also appear to be in danger. Who is the hugger and could he already be inside the Palace walls?.

Porthos uncovers the truth about his parentage and demands answers from his new found father. As he learns more about his past, Porthos questions his place in the Musketeers regiment. However the Musketeers have suspicions about Porthos' new family, wondering whether he should trust them. Can they save Porthos from the dangers that lie ahead and where do his true loyalties lie?.

The Musketeers must put their lives on the line when the Queen is accused of treason. They have no choice but to steal her away from the Palace to safety, while they search for evidence to prove that Rochefort is a Spanish spy. However it soon transpires that nobody is safe from Rochefort's grasp, not even the King, with devastating consequences.

The Musketeers must risk everything to save France from Rochefort's treacherous plan. While Porthos seeks to lure the Spanish spy-master to Paris to prove Rochefort's betrayal to the King, Athos and d'Artagnan must save Constance from certain passing. But will they be able to protect Aramis and the Queen before Rochefort gets to them? The fate of France and their closest comrades lies in the Musketeers' hands.