What happens to a child if a parent is caught with illegal drugs in the house and has a criminal history for drugs?

There is no one clear answer. The police officer would probably contact DHS to have them do an assessment. One obvious question would be where is the other parent? The police might arrest the parent with the drugs and place the child with the other parent, absent some reason not to. Sometimes DHS will work out a safety plan to keep the parent and child together, e.g. if the parent will go immediately into drug treatment. There are many programs that allow children to live with a parent in treatment. (Unfortunately those are mostly programs for women; in-patient treatment programs for dads with their kids are fairly rare.) Another option would be for the parent and child to go live with someone DHS finds trustworthy, like a grandparent (with no criminal record), etc. Policies differ from county to county and even from branch to branch, so there is no universal answer.

If the other parent files a petition to modify the parenting plan based on the drug issue, the court will set conditions for the offending parent, but will allow some contact, usually increasing over time as long as the parent meets the conditions set for him/her.

Child may be removed from the house and custody of the parent.

Basically nothing unless and until the parent is incarcerated or until the child protective services agency gets involved to determine whether the child is abused, neglected or abandoned.

The child will be sheltered and a dependency petition will be filed. The child will be placed with temporary foster care parents until you climb a few mountains to get the child back.

Nothing if no one says anything. Someone should report this to Child Protective Services who will take the child if there are safety issues.

If the actions of the parent are placing the child in danger and the other parent cannot protect the child, Child Protective Services could step in and place the child in protective custody and place the child in foster care. If both parents are in the home and only parent is placing the child in danger, that parent could be forced to leave the home.