Secondary is related to Primary. Primary is a synonym of Chief. Chief is related to Engine. 
Horror is related to Genre. Genre is related to Rock. Rock is related to Driveway. 
Secondary <--RelatedTo--> Primary <--Synonym--> Chief <--RelatedTo--> Engine 
Horror <--RelatedTo--> Genre <--RelatedTo--> Rock <--RelatedTo--> Driveway 