She is gradually befriended by Martha, one of the maids, Ben, the gardener and Dickon, a young boy.  Mary also finds out that she has a bed-ridden cousin, Colin, who thinks he is terminally ill.  Colin is kept locked up in his room and is convinced that his father hates him.

Dickon shows Mary the door to a secret section of the large garden around Craven's house which he himself had closed off after the death of his wife.  Mary eventually convinces Dickon to go into the secret garden and together they start to replant it and take care of it.

Colin joins them in the secret garden when Mary convinces him that nothing is really wrong with him.  He gradually regains his strength and eventually manages to start walking again.  Mr. Craven discovers their little secret but also realizes his mistake in shutting out his son after his wife's death.