She served as the Kingstown-Holyhead mailboat until she was torpedoed and sunk by the German submarine UB-123, which was under the command of Oberleutnant zur See Robert Ramm, on 10 October 1918, while bound for Holyhead.

The exact number of dead is unknown but researchers from the National Maritime Museum of Ireland believe it was at least 564, which would make it the largest single loss of life in the Irish Sea.

[6] Just before 10 a.m. as she was sailing east of the Kish Bank in a heavy swell, passengers saw a torpedo approach from the port side and pass in front of the bow.

The ship made a U-turn in an attempt to return to Kingstown as it began to settle slowly by the bow, but sank rapidly after a third torpedo struck, causing a huge explosion.

Among them were Michael Joyce, an Irish Parliamentary Party MP for Limerick City, and Captain Hutchinson Ingham Cone of the United States Navy, the former commander of the USS Dale (DD-4).

On October 18, 1918 at 9.10 a.m. UB-125, outbound from Germany under the command of Oberleutnant zur See Werner Vater, picked up a radio message requesting advice on the best way to get through the North Sea minefield.

On 10 October 2018 an official commemoration took place in Dún Laoghaire attended by the Minister for Culture, Heritage and the Gaeltacht, Josepha Madigan T.D.