Ann is revealed in the first episode to be a sleeper agent of British Intelligence, Erik having been a broken-down drunk whom she was made to marry as part of her cover story.

In the second series the British Intelligence aspect is developed, until a clash with Soviet and Chinese agents results in both Ann and Erik having to leave Crete.

In the final scene, about to board a plane leaving Heraklion airport, they have a partial reconciliation, since each is the only person the other can trust.

Ann Shepherd was originally meant to be played by Hendry's then-wife Janet Munro, but their marriage ended and she withdrew.

The series' theme is "Ta Trena Pou Fyghan" (Τα Τραίνα Που Φύγαν" = "The Trains That Departed), from the album Hellespont, composed by Stavros Xarchakos.