What happened to Jones when he found himself in the forest?
When Jones reaches the forest at nightfall he enters and encounters figures from his own past and figures from a collective past. His experiences in the forest represent some of his personal mistakes and rash decisions but also represent a history of desperation, indoctrination and exploitation/enslavement.
Jones first encounters the ghost of the man that he killed at a dice game. Then he comes across the Pullman porter he killed too. These men are figures of a personal history and also figures with a specific set of associations for Jones ranging from suppressed guilt and remorse to terror. Importantly, Jones is encountering characters that can be seen as part of his identity (having shaped his life and sent him to prison, etc.) and they can be taken as figures of Jones’ subconscious mind.
As he passes further into the forest, the notion of the forest as a symbol of the subconscious mind becomes strengthened as Jones is stripped of his clothing, discarding his shoes while his clothes are torn to shreds on the tree branches and shrubs.
Jones: I’m meltin’ wid heat! Runnin’ an’ runnin’ an’ runnin’! Damn dis heah coat! Like a strait-jacket! [He tears off his coat and flings it away from him, revealing himself stripped to the waist.]
Stripped down to a relatively bare state, Jones faces specters of his own past that connect him to a larger, collective past. Auction blocks and slave ships appear to him along with a church pulpit.
"And as Jones re-enacts in the forest the horrors of the slave trade that brought Africans to America, O’Neill’s implication is that Jones is also a victim of American racism" (eNotes).
In each scene, Jones is facing an aspect of the experience of black Americans relating to the commerce, ideology and disempowerment that marked that experience. All the episodes of personal and his ethnic history serve to harass and dismay him as Jones travels deeper into the forest (which, again, can be taken as a symbol of his own subconscious mind).
Jones had tried to escape that history and had tried to seize power on this island. The past proves too strong – both his own past and the powerful cultural traditions of the island natives – and Jones is undone in his efforts toward escape.