When sixty-nine-year-old spinster Arabella Pettygrew plunges from the roof of her apartment in Balmoral Square Mansions, there are three possibilities: a tragic accident, suicide, or murder.

Cycling Detective Inspector Richard Strawberry and Constable Brenda Gunn are assigned to the case, but as their investigations unfold, the mystery deepens.

Is there a connection between the pensioner's death and the undercover surveillance being conducted by police in the Square's private gardens? If Arabella is the victim of foul play, the list of suspects is long, including a gallimaufry of eccentric neighbours hiding dark secrets behind their twitching net curtains.

Meanwhile, the Seagull Slayer - a self-appointed crusader on a mission to rid Edinburgh's streets of the 'flying rats' - harbours a murderous hatred for First Minister Nicola Sturgeon which complicates matters even further for Strawberry and Gunn.