The flare, accompanied by the eerie sound of a ship's horn rising above the howling gale, was spotted by villagers in the fishing communities on the famously treacherous rocky outcrop.
The 524 passengers and crew crowded on board the stricken SS Suevic did not yet know it but the largest - and perhaps the greatest - forgotten rescue in the 183-year history of the RNLI had begun.
During the ensuing 16 hours, the 60 crewmen of four wooden lifeboats stationed around the Lizard made multiple journeys in dense fog and towering seas to bring to safety 456 men, women and children on board the stricken liner. Incredibly, not a single life was lost.
The 12,000-ton Suevic, owned by the White Star Line which two years later commissioned the SS Titanic, was on the final leg of a voyage from Australia to Southampton on 17 March 1907 when it hit the Maenheere Reef - a belt of half-submerged rocks a mile off the Lizard.
The subsequent rescue was accomplished with remarkable feats of bravery and sang froid, from the village woman who waded into the waves in darkness to bring children to shore, to the captain of the Suevic who conducted the evacuation while calmly smoking his cigar, not once letting the ash fall to the ground, and to the Cornish vicar who found himself leading the rescue from one of the boats.
But although the lifeboatmen and inhabitants of the Lizard were feted at the time for a feat unsurpassed in the history of the charity, it has taken the 100th anniversary of the wrecking of the Suevic to resurrect the story of derring-do that had since faded from popular memory.
The events of that night will be formally recognised today for the first time since 1907 at a ceremony organised by the RNLI when a commemorative certificate will be presented to the current Lizard lifeboat crew.
Technology from satellite guidance to carbon-fibre self-righting vessels offers modern RNLI crews the safest environment possible for their hazardous work. This equipment proved vital to the successors of the Suevic's rescuers in January when the Lizard lifeboat was involved in the operation to save the crew of the grounded cargo ship, MSC Napoli.
A century ago, there were no such comforts.
When the distress flare was fired from the stricken Suevic, the lifeboatmen from the villages of The Lizard, Cadgwith, Coverack and Porthleven - 15-strong crews - took to four 39ft-long open wooden boats rowed by six oarsmen.
All that the hardy, bearded men, who made their living fishing for pilchard and mackerel, had to protect themselves from the elements were their oilskins and cumbersome cork life belts.
Such was the density of the fog on the night of the rescue and the difficulties caused by a strong south-westerly gale, the crew of the first lifeboat to get to the Suevic only knew they had reached their destination when they smashed into liner's hull, throwing one of them overboard.
Peter Greenslade, current secretary of the Lizard lifeboat, said: "We know that at times the rowers were barely stemming the tide as they pulled against the prevailing conditions. They were in open boats and at the mercy of the sea. It must have been terrifying and yet they went back to the Suevic time and time again."
The rescue operation involved the lifeboats rowing up to four miles out to the liner, which was lodged on rocks but did not sink, and taking on board passengers and crew as the vessels rode the waves. Those on board the Suevic included 85 children, of whom 60 were younger than three. The passengers were ferried to the nearby Polpeor Cove, where women from the village of The Lizard had lit fires to guide the lifeboats and warm the survivors.
An official RNLI history of the incident recorded how two crewmen on the Suevic distinguished themselves in the perilous procedure to load the infants into the waiting lifeboats.
It said: "They carried the children down the rope ladders and when the lifeboats, which were surging up and down, rose on the waves, dropped them into the arms of the lifeboatmen, who tended them until the mothers were lowered over the side and, steadied by the men, were also skilfully dropped into the boats."
One of the two sailors, George Anderson, said afterwards: "It was trying task but, lord, to see those mothers clasp their bairns to their breasts and to hear their thanks and 'God bless you', well, it made me feel that I could have swum ashore with all the babies in the ship."
The records show that the lifeboats from the Lizard and Cadgwith were the first on the scene, arriving just in time to prevent a disaster as two of the Suevic's own lifeboats began an attempt to row to land through narrow channels on the reef known only to locals.
A letter detailing the rescue from Howard Rowley, the RNLI's inspector of lifeboats, showed the charity was in no doubt about the heroism of the rescuers.
Mr Rowley said: "On the arrival of the Cadgwith and Lizard lifeboats, it was found two of the ship's boats were being sent ashore with women and children and, not being acquainted with the dangerous rocks existing in the vicinity, were in the utmost peril.
"Had the lifeboats not been at hand they would doubtless never have reached the shore. Such heroic acts deserve to be brought to the notice of all British people."
Prominent among the rescuers was the Rev Harry Vyvyan, a vicar in Cadgwith and secretary of the village's lifeboat - an honorary position that did not normally involve putting out to sea.
On this occasion, the vicar was determined to take part. He jumped from the Cadgwith lifeboat on to one of the two ship's boats and safely guided it back to land.
When he tried to return to the Suevic with that boat, the sailors were unable to cope and it was smashed on the rocks. Unperturbed, the Rev Vyvyan swam back to shore and waited for the Lizard lifeboat to return, whereby he "proceeded to the wreck where he assisted generally and superintended taking the passengers on board".
Describing how he steered the Suevic lifeboat to shore, he said: "I went on board to steer her but soon found the six men could hardly pull against the wind.
"I can tell you I felt jolly proud when she touched the beach and all the women and children were landed safely. Directly I landed my passengers, I stood up in the bows of the boat and called for volunteers to go back with me."
The rescue continued through the night, with no let-up between 3am and 4am "when the weather was foulest", until the last passenger was brought to safety at midday the next day.
Together, the four RNLI lifeboats saved 456 people. The remaining 68 passengers and crew were taken on board three tug vessels sent by White Star to salvage its stranded liner.
With understatement, the RNLI history stated: "The indomitable pluck and perseverance displayed by all during the service was much appreciated."
Six of rescuers, including Harry Vyvyan and the two crewmen from the Suevic, were given the RNLI's silver medal - its second highest award for gallantry.
Bob Drew, 58, a retired police officer whose family came from Cadgwith, had three relatives on the crew of the village's lifeboat that night. His great-great-uncle, Edwin Rutter, was the coxswain of the vessel and one of those to receive the silver medal.
Mr Drew said: "These were blokes who earned their living as fishermen. They knew the seas backwards but they didn't know what they were going to find after that flare went up.
"I think they were incredibly brave to head off in that thick fog and darkness when they knew the dangers they would face. It tell you all you need to know that the first person to be rescued was the crew member who fell off the lifeboat because it crashed into the hull of Suevic."
The empty liner suffered an unusual fate. Reluctant to write off its vessel, White Star Line commissioned salvagers to sever the bow of the liner stuck on the rocks by blowing it up with dynamite.
The remainder of the ship, which was still afloat, was then towed to Southampton, where it was fitted with a new bow made by Harland & Wolff, the Belfast shipyard that two years later began work on a new White Star commission - SS Titanic. Renamed Skytteren, the Suevic was eventually scuttled by its crew in 1940 off the Swedish coast to prevent capture by the Nazis.
But as dignitaries gather on Lizard Point today for the ceremony overlooking the site of the 1907 rescue, the bravery of other unsung heroes will be remembered alongside that of the lifeboatmen. In its edition of 21 March 1907, The West Briton, the local newspaper, paid a glowing tribute to the Captain Jones, the master of the Suevic.
Its correspondent wrote: "Was there any suggestion of a panic? None whatever. I have never seen better behaviour in my life. One must remember the cigar of Captain Jones. If anything could stop a panic it would be a man who could keep the ash on the end of his cigar in a gale and an emergency."
The newspaper also wrote: "The bravery and self-sacrifice of the women of Cadgwith came in for much commendation. They worked like slaves in turning the winch with drew the lifeboats ashore, and one woman was most heroic, rushing into the sea to her waist and carrying the children ashore. The pluck displayed by the women ... was simply grand."