Sentence:  She paused and took a defiant breath. ‘If you don't believe me, I can't help it. But I'm not a liar.' ¶ ‘No,' said Luke, grinning at her. ‘You're not <WSD>dull</WSD> enough! […] What about the kid's clothes? I don't suppose they were anything to write home about, but didn't you keep anything? A bootee or a bit of embroidery or anything at all?' 
Meaning of the word marked with <WSD> tags:  Not bright or intelligent; stupid; slow of understanding.