A Case of Intrigue in Islington. A Freddy Pilkington-Soames Adventure, #8

During a disturbance at an agricultural show in London, a young man of foreign appearance is stabbed, his killer melting away into the crowd. First on the scene is reporter Freddy Pilkington-Soames, who's covering the show for his newspaper and is just in time to hear the victim's last words, warning of danger to a person by the name of Longstaff and begging Freddy to help. Following a second suspicious death, and with only the young man's message and a crumpled newspaper clipping to guide him, Freddy finds himself embroiled in a mystery that becomes increasingly puzzling the more he looks into it.
Who was the foreigner, and who wanted him dead? How did he know Longstaff was in danger? And what is the significance of the word "Rosa", which was on his lips as he died?Having exasperated his editor one too many times, Freddy's hanging onto his job by the skin of his teeth, but this is a mystery he can't let go. With ruthless and dangerous criminals on his trail who have no hesitation in using violence to achieve their ends, Freddy is in a race against time to prevent a crime that could have a devastating impact and cause misery for thousands of people.
But how can he succeed when he doesn't even know what that crime is?