Trying to find a book title.. help please

tonycommander

This is a book i read a long time ago,  so i will include as many details as i can.. which wont be many I'm afraid...

It was set during ( i suspect ) WW2, and snippets of the story include...

A UK government test of a chemical weapon on a remote scottish island, killing sheep and one falls off a cliff - possibly nearly giving the game away.

The 'hero', who may have been American goes to Germany under cover - hes a doctor i believe.

Perhaps ends up in Berlin.. maybe, theres an incident with another spy being fed to the lions enclosure in the zoo..

the Dr meets a girl, and they both escape - initially on a train and then by foot through holland and end up back in england.

and then she gets shot by a german spy..


All very sketchy memories, but hopefully someone has read it!!!!