When Henry McCabe arrived to work on the gardens at La Mancha, a large country house in Malahide, Co Dublin, he quickly discovered things weren’t right.

It was shortly after 8am and smoke billowed from each of the chimneys, but there were no signs that his employers, the McDonnell siblings, were awake.

“It soon seemed to him that the smoke issuing from the top of the house was excessive and he made to go in at the back door,” reads a report in The Irish Times a day later, on April 1st, 1926. “He saw flames and other signs that things were not as they should be, and he set off at once for Malahide to call the fire brigade, and, on his way, told men whom he met that the house was on fire.”

La Mancha was a prominent building on about 30 acres of “prime land” and was “pleasantly situated and well-kept residence, not of mansion proportions”. Four middle-aged siblings of the McDonnell family had lived there for about six years, having bought it after retiring from a successful grocery, drapery and general store business in Ballygar, Co Galway. The house had recently been put up for sale, with the first mention of the house in The Irish Times appearing days before in a short advertisement.

Before the fire brigade arrived, a Garda sergeant and a local man reached the house and broke into a basement room - that of the family’s yardman, James Clarke. They found him partially dressed on his bed and on dragging him out through the window, saw he was dead.

James had what looked like defensive wounds on his forearms and one deep wound across the left front of his skull, “and from later indications it would seem that his head had been opened by the blow of a poker or some such instrument.” He had been dead for some time.

Firefighters arrived just before 9am and lines of hose were laid from a nearby pond, according to early reports. Water was pumped into the rooms and over the roof of the house, but “the whole of the roof was eventually burned and fell in”. Most of the interior, too, was gutted.

The remains of the McDonnells - Annie (56), Joseph (55), Peter (51) and Alice (47) were recovered, along with that of Mary McGowan, a house servant. The two sisters were found in the same room and were nearly indistinguishable - the rest of the bodies were found throughout the house.

“Four of the bodies were burned, and actually were being charred by the flames when the Fire Brigade arrived; another body bore marks of violence, and the sixth was found stripped,” reads an early report.

Fire poker

Peter McDonnell’s body was “entirely unclothed, but a woollen singlet and a pair of pants were lying loosely over it. This circumstance is one that gives a peculiar depth to the mystery.” He seemed to be the last in the house to die, yet the “garments had the appearance of having been placed over his body by the hands of another.”

A fire poker, which had what looked like brain matter on it, was found near Peter. From the outset, reports point to “mysterious circumstances”.

“All over the house - and the observations of the firemen as to the course of the burnings were to the same effect - it is plain that fires were started in many separate places, apparently by the spreading and lighting of some inflammable spirit.”

The rumours began. Neighbours theorised as to possible culprits within the house - with “peculiarities” mentioned about Alice in particular. Those close to the family would roundly dismiss any conflict between the siblings and deny there was “real evidence of any predisposition to such an extremity of madness” among any of them.

The mystery drew the close attention of newspapers and holiday makers; hundreds travelled to the house to get a look. A week of fruitless searches ensued and no hard leads could be formed. Subsequent medical reports discovered trace amounts of arsenic in some of the bodies; not lethal doses, but enough to make them weak. Each victim had died before the fire was set, by about 5pm on the Monday, one doctor said.

At the inquest, a family friend named Martin Wall further dispelled any idea of friction within the family. As to whether they had any enemies, he said: “They couldn’t have. . . they were too harmless for that,” according to a report on April 10th.

Suspicion turned then to the gardener, McCabe, who lived with his wife and nine young children in Malahide. He was first detained on April 2nd, three days after the fire.

While in custody, he made a statement to police, detailing a story about a safe which had been hidden on the La Mancha property. Shortly after the McDonnells arrived in Malahide, McCabe said he and Clarke were ordered to bury a box near the front porch. Three years later, they were ordered to dig it up and put it in the store.

McCabe was later found to have the keys to the same safe in his pocket when he gave a statement. When police searched the house on the morning of the fire, they found no valuables and it was said some possessions were missing.

Det Sgt John Mooney gave evidence of an encounter with McCabe on the morning of the fire. When he arrived to the scene, he found McCabe standing near the house, smoking a cigarette.

New trousers

“This is an awful business,” the detective said, according to a report on June 29th, to which McCabe replied: “It is, and I after being up all night. They were all right when I left here last night, and when I got here this morning, I got an awful fright: the back door was broken in.”

The door was indeed broken, though it seemed the damage came from the inside. On the same morning, McCabe was also found to be wearing a pair of new, grey trousers that had belonged to Peter McDonnell.

On the day he was officially charged, April 12th, a garda named Hayden asked McCabe how he was: “It is all up with me now,” the gardener said. “I am going to Mountjoy in the morning, and it is all over the pants I have on me. Would I be able to get out and tell my wife to say I got the pants some time ago in a parcel which the McDonnells sent me?” The garda made no reply.

More than 60 witnesses gave evidence of comings and goings to the house over the last days of March. It seemed that McCabe had, on a number of occasions, steered visitors away and said the McDonnells were unwell.

Other evidence included bloodstains on McCabe’s shirt, as well as his access to weed killer, which contained some amount of arsenic. The defence would dismiss the blood stains as common among manual workers and argue that he wouldn’t know how to extract the arsenic from the weed killer: “was McCabe such an expert chemist that he knew?” asked the defence council at the closing of the six-day trial on November 15th, according to a report in the Examiner.

The prosecution’s case, the defence argued, was largely circumstantial. The prosecutor, “could not make bricks without clay, and out of the rotten rubbish and half-baked clay, he was not able to build the house of the prosecution.”

After less than an hour, the jury found McCabe guilty of the six murders.

Asked why he should be spared the death sentence, McCabe, who protested his innocence throughout the trial, said: “All I have to say is God forgive them. I am the victim of bribery and perjury.”

He was sentenced to hang on December 9th, 1926.

The last mention of Henry McCabe in The Irish Times comes seven years later in October 1933, when a boy named Denning found jewellery inscribed “James Clarke” and “J McD” while digging in a garden on Church road, near where McCabe lived. The executed gardener had also reportedly planted the shrubs that were growing in the same garden.

This story is part of the Lost Leads series - a revisiting of lesser-known stories that have made the pages of The Irish Times since 1859. What can you find? Let us know on Twitter: @irishtimes or @deanruxton. For more information on subscribing to the archive, see www.irishtimes.com/archive