"It cannot be otherwise than that Pierre and Paul Lanier are in London, occupying the basement room down those old stairs. Paul makes these night trips up the Thames to scene of his crimes. His conduct stamps him as the murderer of Alice Webster and Oswald Langdon."
Sir Donald holds his peace while shrewd guesses are made as to causes of such suggestive actions.
Still referring to his memoranda, the chief continues:
"Paul is partially deranged. The bodies pitched over the steep bank, and he imagines will escape. Knowing that Alice Webster had been rescued from the lake, he fears she may rise from Thames depths. Pausing at shrubbery along the shore and scrutinizing of projecting branches is through knowledge of how she was saved from that lake immersion. Perhaps Paul is sane on all subjects except the murders. Even as to these he may manifest much craft. Such crazed freaks sooner or later will lead to sure exposure. Pierre knows his son's disordered mental state. It is only necessary that both be well watched. Paul's irresponsible craze will do the rest. The 'lay' of this spy can only be surmised. Perhaps these villains are suspected of other crimes. It is improbable that any self-constituted detective is on their trails. However, this sleuth will be persistently shadowed. It is possible that thereby some important 'find' may occur. By such course our bureau will hedge against all interference."
Sir Donald is greatly encouraged. That the agency fully believes in murder of Oswald Langdon by Paul Lanier is immaterial. The death of Alice Webster is only too certain. Paul thinks he has slain both. It is not strange if thoughts of his awful crimes have caused at least partial madness. Sir Donald says: "This homicidal mania may lead to queer freaks. There are no reliable rules to follow in treatment of such a man. It will be necessary to guard against every possible surprise. Paul must be so carefully and constantly watched as to render his being at large harmless. Otherwise, more deaths may be chargeable to his account."
The chief agrees, and replies:
"It will not do for you or your daughter to remain in London. Sight of either of you might cause the Laniers to leave. Stay of these villains in London will promote exposure of their crimes through Paul's mad infatuation. It is possible Paul sometimes may appear in vicinity of Northfield. There is no telling but that his disordered fancy may find material in former lake memories."
Sir Donald sees the force of these suggestions. He will employ guards at Northfield and along shores of the lake. Father and daughter go home that afternoon. As if in reverie, he says:
"I feel renewed confidence in the London agency. There have been many obstacles. The system employed was faultless. It is unreasonable to judge by the results. Have not my own most subtle, well-matured plans proved unavailing? You never thought of taking part in this scheming for man-capture, yet every important link discovered should be credited to your sweet infatuation. I hardly have treated this agency with proper consideration.
"While kept posted by it, I have concealed much. Neither Paris hospital confession, nor Mary Dodge's story, nor strange romance of Oswald Langdon has been hinted at by me.