The child was abducted by his father, which is already a trend that has led to the creation of many public associations in Russia that are implementing the fatherhood of the country. In such a situation, the mother at least needs to legally record the fact of the capture, transfer and retention of the child by the father in order to bring the perpetrator to appropriate responsibility. The claim will help in such fixation. If the child has not been returned and there are excuses, use the arguments from my article "Stockholm syndrome as a form of lying when committing a crime" to convince the Investigative Committee of the Russian Federation and the court that there are signs of a crime in the father's act - kidnapping. Good luck!