So long." Tuppence walked briskly along towards the Serpentine, first glancing at her watch.
Tuppence walked as if she was dragging her heels in slow agony. 
mnli hypothesis: Tuppence walked as if she was dragging her heels in slow agony.  premise: So long." Tuppence walked briskly along towards the Serpentine, first glancing at her watch.