formed　his　opinion　of　Poirot's　ability　was　slow　to　part　from　it。　At　the　barrier　they　were　held　up。　Their　tickets　were　in　charge　of　the　conductor　of　the　train；　a　fact　which　all　three　of　them　had　forgotten。

Poirot's　explanations　were　rapid；　fluent；　and　impassioned；　but　they　produced　no　effect　upon　the　stolid…faced　official。

〃Let　us　get　quit　of　this；〃　said　Van　Aldin　abruptly。　〃I　gather　you　are　in　a　hurry；　Monsieur　Poirot。　For　God's　sake　pay　the　fares　from　Calais　and　let　us　get　right　on　with　whatever　you　have　got　in　your　mind。〃

But　Poirot's　flood　of　language　had　suddenly　stopped　dead；　and　he　had　the　appearance　of　a　man　turned　to　stone。　His　arm　still　outflung　in　an　impassioned　gesture；　remained　there　as　though　stricken　with　paralysis。

〃I　have　been　an　imbecile；〃　he　said　simply。　〃Ma　foi；　I　lose　my　head　nowadays。　Let　us　return　and　continue　our　journey　quietly。　With　reasonable　luck　the　train　will　not　have　gone。〃

They　were　only　just　in　time；　the　train　moving　off　as　Knighton；　the　last　of　the　three；　swung　himself　and　his　suitcase　on　board。

The　conductor　remonstrated　with　them　feelingly；　and　assisted　them　to　carry　their　luggage　back　to　their　partments。　Van　Aldin　said　nothing；　but　he　was　clearly　disgusted　at　Poirot's　extraordinary　conduct。

Alone　with　Knighton　for　a　moment　or　two；　he　remarked：

〃This　is　a　wild　goose　chase。　The　man　has　lost　his　grip　on　things。　He　has　got　brains　up　to　a　point；　but　any　man　who　loses　his　head　and　scuttles　round　like　a　frightened　rabbit　is　no　earthly　darned　good。〃

Poirot　came　to　them　in　a　moment　or　two；　full　of　abject　apologies　and　clearly　so　crestfallen　that　harsh　words　would　have　been　superfluous。

Van　Aldin　received　his　apologies　gravely；　but　managed　to　restrain　himself　from　making　acid