Grant Newbury, Deputy Inspector of Immigration at the US/Mexico border is asked by his boss to infiltrate a gang smuggling Chinese workers through the border at Calexico, in order to identify and arrest their ringleader. Meanwhile, in Chicago, Estelle Halloway is disappointed because her guardian wrote that she would not be able to spend her holidays with him in Calexico as planned. When she wires him that she will come nevertheless with her room-mate Marguerite and her brother, he tells her that they will meet instead neat the Grand Canyon as it is too warm in Calexico.