ked　in　one　of　the　swings。　　The　glory　of　heaven　deepened　and　darkened　around　the　sublime　vulgarity　of　man；　and　standing　on　the　slope　and　looking　across　the　valley；　Valentin　beheld　the　thing　which　he　sought。　　　　　Among　the　black　and　breaking　groups　in　that　distance　was　one　especially　black　which　did　not　breaka　group　of　two　figures　clerically　clad。　　Though　they　seemed　as　small　as　insects；　Valentin　could　see　that　one　of　them　was　much　smaller　than　the　other。　Though　the　other　had　a　student's　stoop　and　an　inconspicuous　manner；　he　could　see　that　the　man　was　well　over　six　feet　high。　　He　shut　his　teeth　and　went　forward；　whirling　his　stick　impatiently。　　By　the　time　he　had　substantially　diminished　the　distance　and　magnified　the　two　black　figures　as　in　a　vast　microscope；　he　had　perceived　something　else；　something　which　startled　him；　and　yet　which　he　had　somehow　expected。　　Whoever　was　the　tall　priest；　there　could　be　no　doubt　about　the　identity　of　the　short　one。　　It　was　his　friend　of　the　Harwich　train；　the　stumpy　little　cure　of　Essex　whom　he　had　warned　about　his　brown　paper　parcels。　　　　　Now；　so　far　as　this　went；　everything　fitted　in　finally　and　rationally　enough。　　Valentin　had　learned　by　his　inquiries　that　morning　that　a　Father　Brown　from　Essex　was　bringing　up　a　silver　cross　with　sapphires；　a　relic　of　considerable　value；　to　show　some　of　the　foreign　priests　at　the　congress。　　This　undoubtedly　was　the　〃silver　with　blue　stones〃；　and　Father　Brown　undoubtedly　was　the　little　greenhorn　in　the　train。　　Now　there　was　nothing　wonderful　about　the　fact　that　what　Valentin　had　found　out　Flambeau　had　also　found　out；　Flambeau　found　out　everything。　　Also　there　was　nothing　wonderful　in　the　fact　that　when　Flambeau　heard　of　a　sapphire　cross　he　should　try　to　steal　it；　that　was　the　most　natural　thing　in　all　natural　history。　　And　most　certainly　there　was　nothing　wonderful　about　the　fact　that　Flambeau　should　have　it　all　his　own　way　with　such　a　silly　sheep　as　the　man　with　the　umbrella　and　the　parcels。　He　was　the　sort　of　man　whom　anybody　could　lead　on　a　string　to　the　North　Pole；　it　was　not　surprising　that　an　actor　like　Flambeau；　dressed　as　another　priest；　could　lead　him　to　Hampstead　Heath。　　So　far　the　crime　seemed　clear　enough；　and　while　the　detective　pitied　the　priest　for　his　helplessness；　he　almost　despised　Flambeau　for　condescending　to　so　gullible　a　victim。　　But　when　Valentin　thought　of　all　that　had　happened　in　between；　of　all　that　had　led　him　to　his　triumph；　he　racked　his　brains　for　the　smallest　rhyme　or　reason　in　it。　　What　had　the　stealing　of　a　blue…and…silver　cross　from　a　priest　from　Essex　to　do　with　chucking　soup　at　wall　paper？　　What　had　it　to　do　with　calling　nuts　oranges；　or　with　paying　for　windows　first　and　breaking　them　afterwards？　　He　had　come　to　the　end　of　his　chase；　yet　somehow　he　had　missed　the　middle　of　it。　　When　he　failed　（which　was　seldom）；　he　had　usually　grasped　the　clue；　but　nevertheless　missed　the　criminal。　　Here　he　had　grasped　the　criminal；　but　still　he　could　not　grasp　the　clue。　　　　　The　two　figures　that　they　followed　were　crawling　like　black　flies　across　the　huge　green　contour　of　a　hill。　　They　were　evidently　sunk　in　conversation；　and　perhaps　did　not　notice　where　they　were　going；　but　they　were　certainly　going　to　the　wilder　and　more　silent　heights　of　the　Heath。　　As　their　pursuers　gained　on　them；　the　latter　had　to　use　the　undignified　attitudes　of　the　deer…stalker；　to　crouch　behind　clumps　of　trees　and　even　to　crawl　prostrate　in　deep　grass。　　By　these　ungainly　ingenuities　the　hunters　even　came　close　enough　to　the　quarry　to　hear　the　murmur　of　the　discussion；　but　no　word　could　be　distinguished　except　the　word　〃reason〃　recurring　frequently　in　a　high　and　almost　childish　voice。　　Once　over　an　abrupt　dip　of　land　and　a　dense　tangle　of　thickets；　the　detectives　actually　lost　the　two　figures　they　were　following。　They　did　not　find　the　trail　again　for　an　agonising　ten　minutes；　and　then　it　led　round　the　brow　of　a　great　dome　of　hill　overlooking　an　amphitheatre　of　rich　and　desolate　sunset　scenery。　　Under　a　tree　in　this　commanding　yet　neglected　spot　was　an　old　ramshackle　wooden　seat。　　On　this　seat　sat　the　two　priests　still　in　serious　speech　together。　　The　gorgeous　green　and　gold　still　clung　to　the　darkening　horizon；　but　the　dome　above　was　turning　slowly　from　peacock…green　to　peacock…blue；　and　the　stars　detached　themselves　more　and　more　like　solid　jewels。　　Mutely　motioning　to　his　followers；　Valentin　contrived　to　creep　up　behind　the　big　branching　tree；　and；　standing　there　in　deathly　silence；　heard　the　words　of　the　strange　priests　for　the　first　time。　　　　　After　he　had　listened　for　a　minute　and　a　half；　he　was　gripped　by　a　devilish　doubt。　　Perhaps　he　had　dragged　the　two　English　policemen　to　the　wastes　of　a　nocturnal　heath　on　an　errand　no　saner　than　seeking　figs　on　its　thistles。　　For　the　two　priests　were　talking　exactly　like　priests；　piously；　with　learning　and　leisure；　about　the　most　aerial　enigmas　of　theology。　　The　little　Essex　priest　spoke　the　more　simply；　with　his　round　face　turned　to　the　strengthening　stars；　the　other　talked　with　his　head　bowed；　as　if　he　were　not　even　worthy　to　look　at　them。　　But　no　more　innocently　clerical　conversation　could　have　been　heard　in　any　white　Italian　cloister　or　black　Spanish　cathedral。　　　　　The　first　he　heard　was　the　tail　of　one　of　Father　Brown's　sentences；　which　ended：　〃。。。　what　they　really　meant　in　the　Middle　Ages　by　the　heavens　being　incorruptible。〃　　　　　The　taller　priest　nodded　his　bowed　head　and　said：　　　　　〃Ah；　yes；　these　modern　infidels　appeal　to　their　reason；　but　who　can　look　at　those　millions　of　worlds　and　not　feel　that　there　may　well　be　wonderful　universes　above　us　where　reason　is　utterly　unreasonable？〃　　　　　〃No；〃　said　the　other　priest；　〃reason　is　always　reasonable；　even　in　the　last　limbo；　in　the　lost　borderland　of　things。　　I　know　that　people　charge　the　Church　with　lowering　reason；　but　it　is　just　the　other　way。　　Alone　on　earth；　the　Church　makes　reason　really　supreme。　　Alone　on　earth；　the　Church　affirms　that　God　himself　is　bound　by　reason。〃　　　　　The　other　priest　raised　his　austere　face　to　the　spangled　sky　and　said：　　　　　〃Yet　who　knows　if　in　that　infinite　universe？〃　　　　　〃Only　infinite　physically；〃　said　the　little　priest；　turning　sharply　in　his　seat；　〃not　infinite　in　the　sense　of　escaping　from　the　laws　of　truth。〃　　　　　Valentin　behind　his　tree　was　tearing　his　fingernails　with　silent　fury。　　He　seemed　almost　to　hear　the　sniggers　of　the　English　detectives　whom　he　had　brought　so　far　on　a　fantastic　guess　only　to　listen　to　the　metaphysical　gossip　of　two　mild　old　parsons。　　In　his　impatience　he　lost　the　equally　elaborate　answer　of　the　tall　cleric；　and　when　he　listened　again　it　was　again　Father　Brown　who　was　speaking：　　　　　〃Reason　and　justice　grip　the　remotest　and　the　loneliest　star。　Look　at　those　stars。　　Don't　they　look　as　if　they　were　single　diamonds　and　sapphires？　　Well；　you　can　imagine　any　mad　botany　or　geology　you　please。　　Think　of　forests　of　adamant　with　leaves　of　brilliants。　　Think　the　moon　is　a　blue　moon；　a　single　elephantine　sapphire。　　But　don't　fancy　that　all　that　frantic　astronomy　would　make　the　smallest　difference　to　the　reason　and　justice　of　conduct。　On　plains　of　opal；　under　cliffs　cut　out　of　pearl；　you　would　still　find　a　notice…board；　‘Thou　shalt　not　steal。'〃　　　　　Valentin　was　just　in　the　act　of　rising　from　his　rigid　and　crouching　attitude　and　creeping　away　as　softly　as　might　be；　felled　by　the　one　great　folly　of　his　life。　　But　something　in　the　very　silence　of　the　tall　priest　made　him　stop　until　the　latter　spoke。　When　at　last　he　did　speak；　he　said　simply；　his　head　bowed　and　his　hands　on　his　knees：　　　　　〃Well；　I　think　that　other　worlds　may　perhaps　rise　higher　than　our　reason。　　The　mystery　of　heaven　is　unfathomable；　and　I　for　one　can　only　bow　my　head。〃　　　　　Then；　with　brow　yet　bent　and　without　changing　by　the　faintest　shade　his　attitude　or　voice；　he　added：　　　　　〃Just　hand　over　that　sapphire　cross　of　yours；　will　you？　　We're　all　alone　here；　and　I　could　pull　you　to　pieces　like　a　straw　doll。〃　　　　　The　utterly　unaltered　voice　and　attitude　added　a　strange　violence　to　that　shocking　change　of　speech。　　But　the　guarder　of　the　relic　only　seemed　to　turn　his　head　by　the　smallest　section　of　the　compass。　　He　seemed　still　to　have　a　somewhat　foolish　face　turned　to　the　stars。　　Perhaps　he　had　not　understood。　　Or；　perhaps；　he　had　understood　and　sat　rigid　with　terror。　　　　　〃Yes；〃　said　the　tall　priest；　in　the　same　low　voice　and　in　the　same　still　posture；　〃yes；　I　am　Flambeau。〃　　　　　Then；　after　a　pause；　he　said：　　　　　〃Come；　will　you　give　me　that　cross？〃　　　　　〃No；〃　said　the　other；　and　the　monosyllable　had　an　odd　sound。　　　　　Flambeau　suddenly　flung　off　all　his　pontifical　pretensions。　The　great　robber　leaned　back　in　his　seat　and　laughed　low　but　long。　　　　　〃No；〃　he　cried；　〃you　won't　give　it　me；　you　proud　prelate。　　You　won't　give　it　me；　you　little　celibate　simpleton。　　Shall　I　tell　you　why　you　won't　give　it　me？　　Because　I've　got　it　already　in　my　own　breast…pocket。〃　　　　　The　small　man　from　Essex　turned　what　seemed　to　be　a　dazed　face　in　the　dusk；　and　said；　with　the　timid　eagerness　of　〃The　Private　Secretary〃：　　　　　〃Areare　you　sure？〃　　　　　Flambeau　yelled　with　delight。　　　　　〃Really；　you're　as　good　as　a　three…act　farce；〃　he　cried。　〃Yes；　you　turnip；　I　am　quite　sure。　　I　had　the　sense　to　make　a　duplicate　of　the