The primary relationship in '' There Will Be Blood '' is between Daniel Day-Lewis 's character , Daniel Plainview , and his young son , H. W. After casting calls in both New York and Los Angeles , Ms. Sellar said , Mr. Anderson found the perfect H. W. in Dillon Freasier , a 10-year-old boy from Fort Davis , Tex . '' Paul 's always been very much into casting real people , '' Ms. Sellar said . ''