I grabbed my rucksack and walking stick and headed off too, even though I didn't trust the leader - but what could I do?

headed 是动词 head 的过去式，head 在这里的意思是"朝...方向前进"。 off 是副词，表示"离开、出发"的意思。 headed off 是一个短语动词，意思是"出发、启程"，通常指开始一段旅程或离开某个地方。