here　was　no　danger　of　his　recognizing　the　maid　in　the　mistress's　clothing；　but　there　was　the　danger　that　when　he　came　to　discover　the　body　he　might　realize　it　was　not　the　woman　he　had　talked　to　the　night　before。　And　now　we　see　the　reason　for　the　disfigured　face。　The　chief　danger　that　Ada　Mason　ran　was　that　Katherine　Grey　might　visit　her　partment　after　the　train　left　Paris；　and　she　provided　against　that　difficulty　by　ordering　a　dinner　basket　and　by　locking　herself　in　her　partment。〃

〃But　who　killed　Ruth　…　and　when？〃

〃First；　bear　it　in　mind　that　the　crime　was　planned　and　undertaken　by　the　two　of　them　…　Knighton　and　Ada　Mason；　working　together。　Knighton　was　in　Paris　that　day　on　your　business。　He　boarded　the　train　somewhere　on　its　way　round　the　ceinture。　Mrs　Kettering　would　be　surprised；　but　she　would　be　quite　unsuspicious。　Perhaps　he　draws　her　attention　to　something　out　the　window；　and　as　she　turns　to　look　he　slips　the　cord　round　her　neck　…　and　the　whole　thing　is　over　in　a　second　or　two。　The　door　of　the　partment　is　locked；　and　he　and　Ada　Mason　set　to　work。　They　strip　off　the　dead　woman's　outer　clothes。　Mason　and　Knighton　roll　the　body　up　in　a　rug　and　put　it　on　the　seat　in　the　adjoining　partment　amongst　the　bags　and　suitcases。　Knighton　drops　off　the　train；　taking　the　jewel…case　containing　the　rubies　with　him。　Since　the　crime　is　not　supposed　to　have　been　mitted　until　nearly　twelve　hours　later　he　is　perfectly　safe；　and　his　evidence　and　the　supposed　Mrs　Kettering's　words　to　the　conductor　will　provide　a　perfect　alibi　for　his　acplice。

〃At　the　Gare　de　Lyon　Ada　Mason　gets　a　dinner　basket；　and　shutting　herself　into　the　toilet　partment　she　quickly　changes　into　her　mistress's　clothes；　adjusts　two　false　bunches　of　auburn　curls；　and　generally　makes　up　to　resemble　he