ought　I　to　tell　him　how　sorry　I　am　and　all　that　sort　of　thing？　It　seems　so
  dashed　inadequate。〃
  〃I　shouldn't　bother；〃　said　Antony。
  Cayley　nodded　as　he　came　to　them；　and　stood　there　for　a　moment。
  〃We　can　make　room　for　you；〃　said　Bill；　getting　up。
  〃Oh；　don't　bother；　thanks。　I　just　came　to　say；〃　he　went　on　to　Antony；
  〃that　naturally　they've　rather　lost　their　heads　in　the　kitchen；　and　dinner
  won't　be　till　half…past　eight。　Do　just　as　you　like　about　dressing；　of　course。
  And　what　about　your　luggage？〃
  〃I　thought　Bill　and　I　would　walk　over　to　the　inn　directly；　and　see　about
  it。〃
  〃The　car　can　go　and　fetch　it　as　soon　as　it　comes　back　from　the　station。〃
  〃It's　very　good　of　you；　but　I　shall　have　to　go　over　myself；　anyhow；　to
  pack　up　and　pay　my　bill。　Besides；　it's　a　good　evening　for　a　walk。　If　you
  wouldn't　mind　it；　Bill？〃
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  〃I　should　love　it。〃
  〃Well；　then；　if　you　leave　the　bag　there；　I'll　send　the　car　round　for　it
  later。〃
  〃Thanks　very　much。〃
  Having　said　what　he　wanted　to　say；　Cayley　remained　there　a　little
  awkwardly；　as　if　not　sure　whether　to　go　or　to　stay。　Antony　wondered
  whether　he　wanted　to　talk　about　the　afternoon's　happenings；　or　whether　it
  was　the　one　subject　he　wished　to　avoid。　To　break　the　silence　he　asked
  carelessly　if　the　inspector　had　gone。
  Cayley　nodded。　Then　he　said　abruptly；　〃He's　getting　a　warrant　for
  Mark's　arrest。〃
  Bill　made　a　suitably　sympathetic　noise；　and　Antony　said　with　a　shrug
  of　the　shoulders；　〃Well；　he　was　bound　to　do　that；　wasn't　he？　It　doesn't
  follow　that　well；　it　doesn't　mean　anything。　They　naturally　want　to　get
  hold　of　your　cousin；　innocent　or　guilty。〃
  〃Which　do　you　think　he　is；　Mr。　Gillingham？〃　said　Cayley；　looking　at
  him　steadily。
  〃Mark？　It's　absurd；〃　said　Bill　impetuously。
  〃Bill's　loyal；　you　see；　Mr。　Cayley。〃
  〃And　you　owe　no　loyalty　to　anyone　concerned？〃
  〃Exactly。　So　perhaps　I　might　be　too　frank。〃
  Bill　had　dropped　down　on　the　grass；　and　Cayley　took　his　place　on　the
  seat；　and　sat　there　heavily；　his　elbows　on　his　knees；　his　chin　on　his　hands；
  gazing　at　the　ground。
  〃I　want　you　to　be　quite　frank；〃　he　said　at　last。　〃Naturally　I　am
  prejudiced　where　Mark　is　concerned。　So　I　want　to　know　how　my
  suggestion　strikes　you　who　have　no　prejudices　either　way。
  〃Your　suggestion？〃
  〃My　theory　that；　if　Mark　killed　his　brother；　it　was　purely　accidental　as
  I　told　the　inspector。〃
  Bill　looked　up　with　interest。
  〃You　mean　that。　Robert　did　the　hold…up　business；〃　he　said；　〃and　there
  was　a　bit　of　a　struggle；　and　the　revolver　went　off；　and　then　Mark　lost　his
  head　and　bolted？　That　sort　of　idea？〃
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  〃Exactly。〃
  〃Well；　that　seems　all　right。〃　He　turned　to　Antony。　〃There's　nothing
  wrong　with　that；　is　there？　It's　the　most　natural　explanation　to　anyone
  who　knows　Mark。〃
  Antony　pulled　at　his　pipe。
  〃I　suppose　it　is；〃　he　said　slowly。　〃But　there's　one　thing　that　worries
  me　rather。〃
  〃What's　that？〃　Bill　and　Cayley　asked　the　question　simultaneously。
  〃The　key。〃
  〃The　key？〃　said　Bill。
  Cayley　lifted　his　head　and　looked　at　Antony。　〃What　about　the　key？〃
  he　asked。
  〃Well；　there　may　be　nothing　in　it；　I　just　wondered。　Suppose　Robert
  was　killed　as　you　say；　and　suppose　Mark　lost　his　head　and　thought　of
  nothing　but　getting　away　before　anyone　could　see　him。　Well；　very　likely
  he'd　lock　the　door　and　put　the　key　in　his　pocket。　He'd　do　it　without
  thinking；　just　to　gain　a　moment's　time。
  〃Yes；　that's　what　I　suggest。
  〃It　seems　sound　enough；〃　said　Bill。　〃Sort　of　thing　you'd　do　without
  thinking。　Besides；　if　you　are　going　to　run　away；　it　gives　you　more　of　a
  chance。〃
  〃Yes；　that's　all　right　if　the　key　is　there。　But　suppose　it　isn't　there？〃
  The　suggestion；　made　as　if　it　were　already　an　established　fact；　startled
  them　both。　They　looked　at　him　wonderingly。
  〃What　do　you　mean？〃　said　Cayley。
  〃Well；　it's　just　a　question　of　where　people　happen　to　keep　their　keys。
  You　go　up　to　your　bedroom；　and　perhaps　you　like　to　lock　your　door　in
  case　anybody　comes　wandering　in　when　you've　only　got　one　sock　and　a
  pair　of　braces　on。　Well；　that's　natural　enough。　And　if　you　look　round
  the　bedrooms　of　almost　any　house；　you'll　find　the　keys　all　ready；　so　that
  you　can　lock　yourself　in　at　a　moment's　notice。　But　downstairs　people
  don't　lock　themselves　in。　It's　really　never　done　at　all。　Bill；　for　instance；
  has　never　locked　himself　into　the　dining…room　in　order　to　be　alone　with
  the　sherry。　On　the　other　hand；　all　women；　and　particularly　servants；　have　a
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  The　Red　House　Mystery
  horror　of　burglars。　And　if　a　burglar　gets　in　by　the　window；　they　like　to
  limit　his　activities　to　that　particular　room。　So　they　keep　the；　keys　on　the
  outside　of　the　doors；　and　lock　the　doors　when　they　go　to　bed。〃　He
  knocked　the　ashes　out　of　his　pipe；　and　added；　〃At　least；　my　mother　always
  used　to。〃
  〃You　mean；〃　said　Bill　excitedly；　〃that　the　key　was　on　the　outside　of　the
  door　when　Mark　went　into　the　room？〃
  〃Well；　I　was　just　wondering。〃
  〃Have　you　noticed　the　other　rooms　the　billiard…room；　and　library；　and
  so　on？〃　said　Cayley。
  〃I've　only　just　thought　about　it　while　I've　been　sitting　out　here。　You
  live　here　haven't　you　ever　noticed　them？〃
  Cayley　sat　considering；　with　his　head　on　one　side。
  〃It　seems　rather　absurd；　you　know；　but　I　can't　say　that　I　have。〃　He
  turned　to　Bill。　〃Have　you？〃
  〃Good　Lord；　no。　I　should　never　worry　about　a　thing　like　that。〃
  〃I'm　sure　you　wouldn't；〃　laughed　Antony。　〃Well；　we　can　have　a　look
  when　we　go　in。　If　the　other　keys　are　outside；　then　this　one　was　probably
  outside　too；　and　in　that　case　well；　it　makes　it　more　interesting。〃
  Cayley　said　nothing。　Bill　chewed　a　piece　of　grass；　and　then　said；
  〃Does　it　make　much　difference？〃
  〃It　makes　it　more　hard　to　understand　what　happened　in　there。　Take
  your　accidental　theory　and　see　where　you　get　to。　No　instinctive　turning
  of　the　key　now；　is　there？　He's　got　to　open　the　door　to　get　it；　and　opening
  the　door　means　showing　his　head　to　anybody　in　the　hall　…　his　cousin；　for
  instance；　whom　he　left　there　two　minutes　ago。　Is　a　man　in　Mark's　state　of
  mind；　frightened　to　death　lest　he　should　be　found　with　the　body；　going　to
  do　anything　so　foolhardy　as　that？〃
  〃He　needn't　have　been　afraid　of　me；〃　said　Cayley。
  〃Then　why　didn't　he　call　for　you？　He　knew　you　were　about。　You
  could　have　advised　him；　Heaven　knows　he　wanted　advice。　But　the　whole
  theory　of　Mark's　escape　is　that　he　was　afraid　of　you　and　of　everybody　else；
  and　that　he　had　no　other　idea　but　to　get　out　of　the　room　himself；　and
  prevent　you　or　the　servants　from　coming　into　it。　If　the　key　had　been　on
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  the　inside；　he　would　probably　have　locked　the　door。　If　it　were　on　the
  outside；　he　almost　certainly　wouldn't。〃
  〃Yes；　I　expect　you're　right；〃　said　Bill　thoughtfully。　〃Unless　he　took
  the　key　in　with　him；　and　locked　the　door　at　once。
  〃Exactly。　But　in　that　case　you　have　to　build　up　a　new　theory
  entirely。〃
  〃You　mean　that　it　makes　it　seem　more　deliberate？〃
  〃Yes；　that；　certainly。　But　it　also　seems　to　make　Mark　out　an　absolute
  idiot。　Just　suppose　for　a　moment　that；　for　urgent　reasons　which　neither
  of　you　know　anything　about；　he　had　wished　to　get　rid　of　his　brother。
  Would　he　have　done　it　like　that？　Just　killed　him　and　then　run　away？
  Why；　that's　practically　suicide　…　suicide　whilst　of　unsound　mind。　No。　If
  you　really　wanted　to　remove　an　undesirable　brother；　you　would　do　it　a
  little　bit　more　cleverly　than　that。　You'd　begin　by　treating　him　as　a　friend；
  so　as　to　avoid　suspicion；　and　when　you　did　kill　him　at　last；　you　would　try
  to　make　it　look　like　an　accident；　or　suicide；　or　the　work　of　some　other　man。
  Wouldn't　you？〃
  〃You　mean　you'd　give　yourself　a　bit　of　a　run　for　your　money？〃
  〃Yes；　that's　what　I　mean。　if　you　were　going　to　do　it　deliberately；　that
  is　to　say　and　lock　yourself　in　before　you　began。〃　Cayley　had　been　silent；
  apparently　thinking　over　this　new　idea。　With　his　eyes　still　on　the　ground；
  he　said　now：　〃I　hold　to　my　opinion　that　it　was　purely　accidental；　and　that
  Mark　lost　his　head　and　ran　away。
  〃But　what　about　the　key？〃　asked　Bill。
  〃We　don't　know　yet　that　the　keys　were　outside。　I　don't　at　all　agree
  with　Mr。　Gillingham　that　the　keys　of　the　down…stairs　rooms　are　always
  outside　the　doors。　Sometimes　they　are；　no　doubt；　but　I　think　we　shall
  probably　find　that　these　are　inside。〃
  〃Oh；　well；　of　course；　if　they　are　inside；　then　your　original　theory　is
  probably　the　correct　one。　Having　often　seen　them　outside；　I　just
  wondered　that's　all。　You　asked　me　to　be　quite　frank；　you　know；　and　tell
  you　what　I　thought。　But　no　doubt　you're　right；　and　we　shall　find　them
  inside；　as　you　say。
  〃Even　if　the　key　was　outside；〃　went　on　Cayley　stubbornly；　〃I　still　think
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  The　Red　House　Mystery
  it　might　have　been　accidental。　He　might　have　taken　it　in　with　him；
  knowing　that　the　interview　would　be　an　unpleasant　one；　and　not　wishing
  to　be　interrupted。〃
  〃But　he　had　just　told　you　to　stand　by　in　case　he　wanted　you；　so　why
  should　he　lock　you　out？　Besides；　I　sho