Episode1-TheEternityRingMI5suspectsBritishatomicresearchhasbeeninfiltrated,andaskFoyletoinvestigatewhetheraRussianspynetworkcouldbeatworkintheheartofLondon.Episode2-TheCageFoyle’sinvestigationintothedeathofanamelessRussianleadstoamysteriousmilitaryfacilityandthediscoverythatthevictimwasaspywithdangerousconnectionstoBritishintelligence.Episode3-SunflowerProfessorPeterVanHarengivesalecturetoagroupofstudentsontheself-portraitsoftheartistRembrandtandcausesayoungmantosufferafrighteningflashbackwhichendsintragedy.