Well there is only one sure-fire way to know exactly how it is wired . . . and that is to look.
If you would like my opinion and that of the other regulars, please take a sequence of photographs that clearly shows (1) the cables present behind each socket, (2) the colours of the wires from each cable and (3) the terminals to which each wire is connected.
Are you
absolutely sure that there are just those two sockets connected to the line? Are there any junction boxes, either indoors or out? Are you fed by an aerial dropwire or an underground service feed cable?