How is vulnerability revealed in Chapter 21 of 'The Go-between'?

Reaching to the end of the story, the narrator can be felt to resurface more frequently and his thoughts become notably inconsistent, often wavering from one thought to the next. For example, Leo's interpretation of Ted's self worth is expressed to be 'carried' on him, making him an easier target than those whose values are 'spread out over houses and parklands', increasing his vulnerability when the notion of being 'killed' enters Leo's thoughts. But then he suggest Marian to be a victim in Ted's 'enticing' behavior.

Vulnerability is predominantly depicted within Leo's journey to, then encountering the 'deadly nightshade'. By repeatedly referring to the 'darkness' that surrounds him, we empathise with his 'fear' of becoming lost, plus the fear of being 'shut' out symbolises his isolation from the higher class social groups. Regularly, his environment has a large impact on the vulnerability felt within him, stating the 'night' was a 'forbidden world', where 'Little boys' are susceptible to 'bad grown-ups'; 'thieves, murderers', all adding to a strong sense of unnerving terror.

Arguably, most is revealed inside Leo's confrontation of the atropa belladonna. He personifies the plant and acts as though he has willingly given into its power; 'it wanted me', further enhancing a sense of command by suggesting it was the one 'preparing' the 'spell', not himself. It seems due to its intimidating nature, Leo is submissive and almost possessed to envelop the plants form; '...I stretched my hand out into the thick darkness...' again Hartley uses 'darkness' to heighten Leo's vulnerability. The plant's inviting quality then becomes so strong, Leo actually steps into its midst. But then formidably senses his fear again and struggles to 'force' his 'way out' by violently tearing and ripping the plant, like prey becoming desperate to escape its predator, corresponding to how sometimes his relationship with Marian has been like.