In Maryland law, both biological parents have joint rights and obligations to their child, unless fixed otherwise by a court order. Thus, a problem arises when the parties are not getting along, but have no court order. Ideally, they would work together, perhaps with the assistance of attorneys, to figure a custody plan for their child as it can take quite a while for a case to move through the court system. Sometimes, however, one of the parties refuses to let the other see the child, or even leaves and goes into hiding with the child.
See, for example, this case from the District of Columbia which has been in the news here for the past year. Thirteen years prior, the father was awarded custody of the parties' four year old girl, and the mother then absconded with her to Delaware. They were not found until last year, and the mother was prosecuted and acquitted of parental kidnapping. This case represents a true tragedy, as the father and daughter barely know each other now, and it may take their whole lifetimes to build a strong relationship.