Crippen, unaware of the good impression he had made on Dew, panicked. He told Ethel of Dew’s visit, and persuaded her that they would need to leave the country for a year, until the scandal surrounding Belle’s desertion had died down. They travelled to Antwerp the following day, to catch a boat bound for Quebec, in Canada.
On a routine follow-up visit to Crippen’s dental practice, on 11 July, Dew discovered that Crippen and Ethel had disappeared. He returned immediately to Hilldrop Crescent, to find that the maid had been dismissed, and was in the process of preparing the house for an extended absence. Dew organised an extremely thorough search of the premises, conducted over two full days, which finally unearthed the rotting remains concealed beneath the floor of the cellar. A medical examination of the remains of the torso found an operation scar, which enabled them to identify the remains as Belle Crippen. They also discovered the presence of Hyoscine. On 16 July an arrest warrant was issued for Hawley Crippen and Ethel le Neve.
The case made huge headlines in England, and the story, with pictures of the fugitives, was carried in European newspapers as well. Crippen decided that they would be best travelling incognito, and he boarded the SS Montrose in Antwerp, bound for Canada, on 20 July 1910, travelling as Mr. Robinson, with Ethel disguised, rather poorly, as his young son. Unfortunately for them, the Captain of the Montrose, named Kendall, took a local newspaper with him, on the day of departure, containing pictures of the fugitives. Ethel’s poor disguise drew attention; looking more closely, Captain Kendall recognised the similarity between the odd couple and the fugitives and, on 22 July, sent a wireless telegram to the White Star Line in Liverpool, claiming that Crippen and Ethel were onboard. It was the first time that this new means of communications was used in the apprehension of a criminal. The information was passed immediately to Inspector Dew at Scotland Yard.
Fortunately for Dew, another White Star liner, the SS Laurentic, was due to leave Liverpool for Quebec the following morning; a faster ship, she would actually arrive at her destination before the SS Montrose. The thrill of the transatlantic chase gripped the media, and newspapers were full of stories about the love triangle, covering the lives of Belle, Ethel and Crippen, and plotting the progress of each ship, as the Laurentic steadily made ground on the Montrose.
The Laurentic reached Quebec the day before the Montrose, as scheduled. When the Montrose reached Father Point, on 31 July 1910, and prepared to take pilots onboard to guide the ship into dock, Dew boarded the vessel, disguised as a pilot, and arrested Hawley Crippen and Ethel le Neve. He was able to do this in his capacity as a Scotland Yard detective, carrying out his duty within British Territorial Waters. Had Crippen decided to sail straight to the United States instead of Canada, Dew would have had no jurisdiction over Crippen, a US citizen, within United States territory.