I　should　have　remembered　afterwards。〃
  〃Perhaps　Cayley　shut　the　door　after　him。〃
  〃Wait！〃
  He　pressed　his　hand　over　his　eyes　and　thought。　It　wasn't　anything
  which　he　had　heard；　but　something　which　he　had　seen。　He　tried
  desperately　hard　to　see　it　again。。。。　He　saw　Cayley　getting　up；　opening　the
  door　from　the　office；　leaving　it　open　and　walking　into　the　passage；　turning
  to　the　door　on　the　right；　opening　it；　going　in；　and　then　…What　did　his
  eyes　see　after　that？　If　they　would　only　tell　him　again！
  Suddenly　he　jumped　up；　his　face　alight。　〃Bill；　I've　got　it！〃　he　cried。
  〃What？〃
  〃The　shadow　on　the　wall！　I　was　looking　at　the　shadow　on　the　wall。
  Oh；　ass；　and　ten　times　ass！〃
  Bill　looked　uncomprehendingly　at　him。　Antony　took　his　arm　and
  pointed　to　the　wall　of　the　passage。
  〃Look　at　the　sunlight　on　it；〃　he　said。　〃That's　because　you've　left　the
  door　of　that　room　open。　The　sun　comes　straight　in　through　the　windows。
  Now；　I'm　going　to　shut　the　door。　Look！　D'you　see　how　the　shadow
  moves　across？　That's　what　I　saw　the　shadow　moving　across　as　the　door
  shut　behind　him。　Bill；　go　in　and　shut　the　door　behind　you　quite　naturally。
  Quick！〃
  Bill　went　out　and　Antony　knelt；　watching　eagerly。
  〃I　thought　so！〃　he　cried。　〃I　knew　it　couldn't　have　been　that。〃
  〃What　happened？〃　said　Bill；　coming　back。
  〃Just　what　you　would　expect。　The　sunlight　came；　and　the　shadow
  moved　back　again　all　in　one　movement。〃
  〃And　what　happened　yesterday？〃
  〃The　sunlight　stayed　there；　and　then　the　shadow　came　very　slowly
  back；　and　there　was　no　noise　of　the　door　being　shut。〃
  Bill　looked　at　him　with　startled　eyes。
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  〃By　Jove！　You　mean　that　Cayley　closed　the　door　afterwards　as　an
  afterthought　and　very　quietly；　so　that　you　couldn't　hear？〃
  Antony　nodded。
  〃Yes。　That　explains　why　I　was　surprised　afterwards　when　I　went　into
  the　room　to　find　the　door　open　behind　me。　You　know　how　those　doors
  with　springs　on　them　close？〃
  〃The　sort　which　old　gentlemen　have　to　keep　out　draughts？〃
  〃Yes。　Just　at　first　they　hardly　move　at　all；　and　then　very；　very　slowly
  they　swing　to　well；　that　was　the　way　the　shadow　moved；　and
  subconsciously　I　must　have　associated　it　with　the　movement　of　that　sort　of
  door。　By　Jove！〃　He　got　up；　and　dusted　his　knees。　〃Now；　Bill；　just　to
  make　sure；　go　in　and　close　the　door　like　that。　As　an　afterthought；　you
  know；　and　very　quietly；　so　that　I　don't　hear　the　click　of　it。〃
  Bill　did　as　he　was　told；　and　then　put　his　head　out　eagerly　to　hear　what
  had　happened。
  〃That　was　it；〃　said　Antony；　with　absolute　conviction。　〃That　was　just
  what　I　saw　yesterday。〃　He　came　out　of　the　office；　and　joined　Bill　in　the
  little　room。
  〃And　now；〃　he　said；　〃let's　try　and　find　out　what　it　was　that　Mr。　Cayley
  was　doing　in　here；　and　why　he　had　to　be　so　very　careful　that　his　friend　Mr。
  Gillingham　didn't　overhear　him。〃
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  CHAPTER　XIII
  The　Open　Window
  Anthony's　first　thought　was　that　Cayley　had　hidden　something；
  something；　perhaps；　which　he　had　found　by　the　body；　and　but　that　was
  absurd。　In　the　time　at　his　disposal；　he　could　have　done　no　more　than　put
  it　away　in　a　drawer；　where　it　would　be　much　more　open　to　discovery　by
  Antony　than　if　he　had　kept　it　in　his　pocket。　In　any　case　he　would　have
  removed　it　by　this　time；　and　hidden　it　in　some　more　secret　place。　Besides；
  why　in　this　case　bother　about　shutting　the　door？
  Bill　pulled　open　a　drawer　in　the　chest；　and　looked　inside。
  〃Is　it　any　good　going　through　these；　do　you　think？〃　he　asked。
  Antony　looked　over　his　shoulder。
  〃Why　did　he　keep　clothes　here　at　all？〃　he　asked。　〃Did　he　ever　change
  down　here？〃
  〃My　dear　Tony；　he　had　more　clothes　than　anybody　in　the　world。　He
  just　kept　them　here　in　case　they　might　be　useful；　I　expect。　When　you　and
  I　go　from　London　to　the　country　we　carry　our　clothes　about　with　us。
  Mark　never　did。　In　his　flat　in　London　he　had　everything　all　over　again
  which　he　has　here。　It　was　a　hobby　with　him；　collecting　clothes。　If　he'd
  had　half　a　dozen　houses；　they　would　all　have　been　full　of　a　complete
  gentleman's　town　and　country　outfit。〃
  〃I　see。〃
  〃Of　course；　it　might　be　useful　sometimes；　when　he　was　busy　in　the
  next　room；　not　to　have　to　go　upstairs　for　a　handkerchief　or　a　more
  comfortable　coat。〃
  〃I　see。　Yes。〃　He　was　walking　round　the　room　as　he　answered；　and
  he　lifted　the　top　of　the　linen　basket　which　stood　near　the　wash　basin　and
  glanced　in。　〃He　seems　to　have　come　in　here　for　a　collar　lately。〃
  Bill　peered　in。　There　was　one　collar　at　the　bottom　of　the　basket。
  〃Yes。　I　daresay　he　would；〃　he　agreed。　〃If　he　suddenly　found　that
  the　one　he　was　wearing　was　uncomfortable　or　a　little　bit　dirty；　or
  something。　He　was　very　finicking。〃
  Antony　leant　over　and　picked　it　out。
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  The　Red　House　Mystery
  〃It　must　have　been　uncomfortable　this　time；〃　he　said；　after　examining
  it　carefully。　〃It　couldn't　very　well　be　cleaner。〃　He　dropped　it　back　again。
  〃Anyway；　he　did　come　in　here　sometimes？〃
  〃Oh；　yes；　rather。〃
  〃Yes；　but　what　did　Cayley　come　in　for　so　secretly？〃
  〃What　did　he　want　to　shut　the　door　for？〃　said　Bill。　〃That's　what　I
  don't　understand。　You　couldn't　have　seen　him；　anyhow。〃
  〃No。　So　it　follows　that　I　might　have　heard　him。　He　was　going　to　do
  something　which　he　didn't　want　me　to　hear。〃
  〃By　Jove；　that's　it！〃　said　Bill　eagerly。
  〃Yes；　but　what？〃
  Bill　frowned　hopefully　to　himself；　but　no　inspiration　came。
  〃Well；　let's　have　some　air；　anyway；〃　he　said　at　last；　exhausted　by　the
  effort；　and　he　went　to　the　window；　opened　it；　and　looked　out。　Then；　struck
  by　an　idea；　he　turned　back　to　Antony　and　said；　〃Do　you　think　I　had　better
  go　up　to　the　pond　to　make　sure　that　they're　still　at　it？　Because　〃
  He　broke　off　suddenly　at　the　sight　of　Antony's　face。
  〃Oh；　idiot；　idiot！〃　Antony　cried。　〃Oh；　most　super…excellent　of
  Watsons！　Oh；　you　lamb；　you　blessing！　Oh；　Gillingham；　you
  incomparable　ass！〃
  〃What　on　earth　…〃
  〃The　window；　the　window！〃　cried　Antony；　pointing　to　it。
  Bill　turned　back　to　the　window；　expecting　it　to　say　something。　As　it
  said　nothing；　he　looked　at　Antony　again。
  〃He　was　opening　the　window！　〃　cried　Antony。
  〃Who？〃
  〃Cayley；　of　course。〃　Very　gravely　and　slowly　he　expounded。　〃He
  came　in　here　in　order　to　open　the　window。　He　shut　the　door　so　that　I
  shouldn't　hear　him　open　the　window。　He　opened　the　window。　I　came　in
  here　and　found　the　window　open。　I　said；　'This　window　is　open。　My
  amazing　powers　of　analysis　tell　me　that　the　murderer　must　have　escaped
  by　this　window。'　'Oh；'　said　Cayley；　raising　his　eyebrows。　'Well；'　said　he；　'I
  suppose　you　must　be　right。'　Said　I　proudly；　'I　am。　For　the　window　is
  open；'　I　said。　Oh；　you　incomparable　ass！〃
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  The　Red　House　Mystery
  He　understood　now。　It　explained　so　much　that　had　been　puzzling
  him。
  He　tried　to　put　himself　in　Cayley's　place　…　Cayley；　when　Antony　had
  first　discovered　him；　hammering　at　the　door　and　crying；　〃Let　me　in！〃
  Whatever　had　happened　inside　the　office；　whoever　had　killed　Robert；
  Cayley　knew　all　about　it；　and　knew　that　Mark　was　not　inside；　and　had　not
  escaped　by　the　window。　But　it　was　necessary　to　Cayley's　plans　…　to
  Mark's　plans　if　they　were　acting　in　concert　…　that　he　should　be　thought　so
  to　have　escaped。　At　some　time；　then；　while　he　was　hammering　（the　key
  in　his　pocket）　at　the　locked　door；　he　must　suddenly　have　remembered　with
  what　a　shock！　that　a　mistake　had　been　made。　A　window　had　not　been　left
  open！
  Probably　it　would　just　have　been　a　horrible　doubt　at　first。　Was　the
  office　window　open？　Surely　it　was　open！　Was　it？。。。。　Would　he　have
  time　now　to　unlock　the　door；　slip　in；　open　the　French　windows　and　slip　out
  again？　No。　At　any　moment　the　servants　might　come。　It　was　too　risky。
  Fatal；　if　he　were　discovered。　But　servants　were　stupid。　He　could　get
  the　windows　safely　open　while　they　were　crowding　round　the　body。
  They　wouldn't　notice。　He　could　do　it　somehow。
  And　then　Antony's　sudden　appearance！　Here　was　a　complication。
  And　Antony　suggesting　that　they　should　try　the　window！　Why；　the
  window　was　just　what　he　wanted　to　avoid。　No　wonder　he　had　seemed
  dazed　at　first。
  Ah；　and　here　at　last　was　the　explanation　why　they　had　gone　the　longest
  way　round　and　yet　run。　It　was　Cayley's　only　chance　of　getting　a　start　on
  Antony；　of　getting　to　the　windows　first；　of　working　them　open　somehow
  before　Antony　caught　him　up。　Even　if　that　were　impossible；　he　must　get
  there　first；　just　to　make　sure。　Perhaps　they　were　open。　He　must　get
  away　from　Antony　and　see。　And　if　they　were　shut；　hopelessly　shut；　then
  he　must　have　a　moment　to　himself；　a　moment　in　which　to　think　of　some
  other　plan；　and　avoid　the　ruin　which　seemed　so　suddenly　to　be　threatening。
  So　he　had　run。　But　Antony　had　kept　up　with　him。　They　had　broken
  in　the　window　together；　and　gone　into　the　office。　But　Cayley　was　not
  done　yet。　There　was　the　dressing…room　window！　But　quietly；　quietly。
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  The　Red　House　Mystery
  Antony　mustn't　hear。
  And　Antony　didn't　hear。　Indeed；　he　had　played　up　to　Cayley
  splendidly。　Not　only　had　he　called　attention