The interrupted conversation

An original fiction passage set in the nineteenth century.

Mr Lyall was describing his plans when the servant brought in a note. He read it once, folded it and continued speaking. Nothing in his words changed, but the warmth had gone from his voice. His visitor asked whether the news was unwelcome. Mr Lyall said it was merely inconvenient and began discussing the train timetable, although a moment earlier he had intended to remain for another week.

Identify the phrase which suggests that the note changes Mr Lyall’s mood.