Sentence:  But when attending the Quaker service, he still encounters a certain 'special' silence: in the wholly undecorated, <WSD>altarless</WSD> room, there is nothing to be heard except 'the crackling of the fireplace and muffled coughing', until, in an odd combination of spontaneity and planning, someone 'moved' by the spirit holds a 'carefully prepared' speech. 
Meaning of the word marked with <WSD> tags:  Not having an altar.