Captain Molineux, a young English officer commanding a detachment at Ballyraggett, Ireland, finds Claire Ffolliott, a Sligo lady, working at a churn outside her cabin home. He at first takes her for a dairymaid, and flirts with her. Then Arte O'Neale appears, and he learns that Claire and Arte are gentlewomen who have been reduced to poverty by the machinations of their enemies. He wants permission to shoot and fish on the estate, but Claire says to Arte: " Shall I spare you the humiliation of confessing that you are not mistress in your own house, much less lady of the manor?" She turns to Molineux. "Do you see that ruin yonder? Oh, 'tis the admiration of the traveller, and the study of painters, who come from far and near to copy it. It was the home of my forefathers when they kept open house for the friend--the poor--or the stranger. The mortgagee has put up a gate now, so visitors pay sixpence a head to admire the place, and their guide points across to the cabin where the remains of the old family, two lonely girls, live--God knows how. You ask leave to kill game on Suil-a-more and Keim-an-eigh." She crosses to the dairy window. "Do you see that salmon? It was snared last night in the pool ... by Conn, the Shaughraun. He killed those grouse at daylight on the side of Maurnturk. That's our daily food, and we owe it to a poacher."
The period is that in which the revolutionary movement known as Fenianism is in full blast. Claire's brother, Robert, as Molineux learns, has been transported to Australia because of his active opposition to British rule. It is because Robert's estate has been practically confiscated during his absence that his sister and her cousin are in their present plight. The situation becomes clear when Corry Kinchela, a scampish squireen, appears on the scene and actually gloats over their plight. "I'm just back from Dublin," he says, "and thought I'd stop in my road to tell you the court has decreed the sale of this estate, under foreclosure, and in two months you'll have to turn out."
Molineux has been ordered by his Government to look out for a "schooner carrying a distinguished Fenian hero" which is said to be "hovering about the coast," intending to land her passengers in the neighborhood. This hero turns out to be none other than Robert Ffolliott who, thanks to the efforts of Conn, the Shaughraun, has succeeded in escaping from Australia by way of America.
In the home of Father Dolan, a local priest, Robert appears in company with his sister, Claire, and his betrothed, Arte. The priest's niece, Moya, is present. Conn is there, too; he conveys by means of his speech, his actions and his demeanor something of the meaning of the word "Shaughraun." (The Shaughraun is the Soul of every Fair, the Life of every Funeral, the First Fiddle at all weddings and patterns.)
Father Dolan disapproves of the drinking habits and irregular life of Conn, but admires his loyalty and his good heart. For Robert Ffolliott he feels the love that a father might feel for his son--and, indeed, the elder Ffolliott when he died had laid a special charge on Dolan to care for his infant son. But even while the priest is rejoicing over the safe return of Robert to Ireland, a sinister figure who had been largely responsible for Robert's arrest and transportation, lurks in the shadows behind the house. It is Harvey Duff, the rascally accomplice of Corry Kinchela.
Never has a man found a truer friend than Robert finds in Conn; and never did a man need a friend more than Robert needs Conn. For Robert is now being stalked as a felon escaping from justice, and Molineux, in performance of his duty, is compelled to arrest him again and take him to prison.
At this juncture, Kinchela receives word that the English Government has granted an amnesty to Fenian prisoners. The news spoils all his plans, for he has hoped to get possession of the Ffolliott estate and to marry Arte O'Neale.
Kinchela and Harvey Duff now conspire to betray Robert by offering him the means of escape from his cell--they plan to shoot him as he makes the attempt. Kinchela visits Robert in his prison, winning his confidence. He asks: "Is that ship that landed you within reach?" Robert replies: "Every night at eight o'clock she runs in shore and lies off the coast; a bonfire lighted on Rathgarron Head is to be the signal for her to send off her skiff under the ruins of St. Bridget's Abbey to take me on board." Kinchela responds: "That signal will be fired tonight, and you shall be there to meet the boat." He hands a pistol to Robert.
When Robert secretly emerges from his cell a few hours later, Kinchela and four constables are waiting behind a wall nearby. Harvey Duff carries a carbine. But just as Duff is getting ready to fire, Conn drops from a wall on Duff's shoulders and throws him to the ground. Conn creates the impression that it is Robert who has fallen, and in the ensuing confusion Conn and Robert make their escape.
On Rathgarron Head that night Conn plays another trick. The bonfire is lighted; Robert swims out to safety. Conn leads the constables on a false trail and receives in his own body the shots intended for his friend. He falls, apparently lifeless, and is carried on a shutter to the cabin of his mother. Over his (supposed) corpse is held a wake which, when Conn comes to his senses, affords him great amusement.
The next step of the vicious Kinchela and Duff is to organize a band of ruffians, and to kidnap Arte O'Neale and her friend Moya, Conn's sweetheart. The two women are held in a shed overlooking a rocky cave on the seacoast. The topmasts of a ship can be seen beyond the edge of a precipice. Kinchela and Duff are planning to take the women to sea.
In the nick of time a mob, headed by Conn, comes to the rescue. Retribution is effected by violently melodramatic means. Harvey Duff leaps to his death over a cliff. Kinchela is hurt but not killed, and is led off to be dealt with by a legal tribunal. Conn receives the permission of Father Dolan to marry Moya, and promises to mend his ways.
Since Robert, the revolutionary, is now released, under the amnesty, and has nothing to fear from either the English soldiery or the Irish constabulary, his troubles for the time being are over. With Conn his friend, Claire his sister, and Arte his betrothed, he is able to enjoy without anxiety the sunlight of freedom.