Sentence:  The case was that of a murder. It had an element of mystery about it, however, which was puzzling the authorities. A turban and loincloth soaked in <WSD>blood</WSD> had been found; also a staff. 
Meaning of the word marked with <WSD> tags:  A vital liquid flowing in the bodies of many types of animals that usually conveys nutrients and oxygen. In vertebrates, it is colored red by hemoglobin, is conveyed by arteries and veins, is pumped by the heart and is usually generated in bone marrow.