In Ontario, both parents have equal rights to access their child. To entirely remove your child from your partners care, you will need a court order that gives you custody. Custody is decided when a judge determines what is in the best interests of your child. If you remove your child from their other parent, it may reflect poorly on you during future litigation. If you feel it is extremely unsafe for yourself and your child to remain with your partner, one way to mitigate this problem is by having a family lawyer help you write a letter to your partner before or right after you leave. This letter can explain that you wish to work out custody and access matters. Ultimately, it is best to speak to a family lawyer before taking steps to take your child with you as you leave your partner.