Investigation is related to Detective. Detective is related to Crime. Crime is a synonym of Offense. 
Deep is related to Vertical. Vertical is related to Steep. Steep is related to Slope. 
Investigation <--RelatedTo--> Detective <--RelatedTo--> Crime <--Synonym--> Offense 
Deep <--RelatedTo--> Vertical <--RelatedTo--> Steep <--RelatedTo--> Slope 