For decades a small Scottish island was a classified death trap after WWII-era testing of biological agents left it completely uninhabitable.

One single year, 80 doomed sheep and a whole lot of bioweapon testing. It’s a list that makes up the critical components of a moment in history when Britain’s dangerous dalliance with biochemical explosives would lead to a decades-long quarantine of a small chunk of rock off the coast of the Scottish Highlands.

That 520-acre abandoned island known as Gruinard was once, in simpler and safer days at least, a popular picnic destination for Scottish families before the start of World War II. During the midst of the war and after two years of relentless bombings by the Germans of industrial and civilian targets, British prime minister Winston Churchill was getting nervous. In one 24-day stretch of what is known as the London Blitz, the German Luftwaffe dropped 5,300 tons of explosives on Britain’s capital city.