Sanbon yubi no otoko

Being acquainted with the bride's uncle, a famed private detective is invited to a wedding ceremony. The groom's family is moneyed and owns large tracts of land. The bride is a former teacher and was rumoured to have had an affair, which explains why the groom's family opposed the union. On the night of the ceremony the bride and groom are killed in a sealed room. There is evidence left, however, as there is a hand print on the wall albeit with only the trace of three fingers.