Andrea made the assassins send Samuel to a far away place instead of killing him to make the first and third wife fight each other over the disappearance of Samuel. The third wife always wanted one of her children to take the crown and kidnapping the competition would be something people would expect her to do to achieve her dream. On the other hand the children of the fifth and other wives were either small or incompetent. The king would not consider them to be in the race for crown.
Andrea showed herself to others as a shallow person without any ambition or capabilities to aim for the crown because she would always talk about looks and money and other superficial things which border towards gossip rather than planning for the crown. But what the others didn't know was that it was all a farce to make others underestimate her. It's because of this reason people would be inclined to think it was the third wife who was responsible for Samuels disappearance rather than Andrea.
She had secretly sent spies to become maids of the other wives. Where as the other wives didn't even bother to care about her. When she came to the palace, the third wife sent some spies to check her real personality. But unknown to her Andrea was expecting this and hence acted the part of being a dumb person to make the spies believe that she had nothing to hide. Later the spies were either caught trying to steal money from her budget or fighting with other maids. All of these were false charges but something which can be expected to happen in the palace so no one thought much about them.
The first wife had the most capable son and the third wife came from the most influential noble family among the wives. So everyone thought they both would give the shot at making their sons the king.It was for this reason Andrea planned on having them fight each other.
She was planning on weakening the other two wives by having their children have "accidents" or have them make a fool out of themselves till one of her children can have a shot at the throne.
Then she would show them her true colours. but for the time being she had to slowly bid her time. She planned on accidently finding Samuel if his brother became the King one day in which case she would be in his good graces.
Everyone on the palace knew that Darton was the likely person to be the king as he was the oldest, had the most capability, was the most liked person in the city. He was already 19 years old so he was a big thorn in her plan but she couldn't have him killed as that would confirm one of the second wife's children for the position of the king.
She didn't suspect Samuel would be able to escape because no one would believe him to be the prince and even if by some chance he was able to return to the royal city then people would suspect the second wife as hamshire was very close to her maternal brothers city.
Her aim was to have Darton and the sons of third wife fight each other and weaken their positions among the nobles and then use her influence and strengthen the position of her sons to make them the future king.
She would also marry off her daughter to the son of the commander of army to further strengthen the position of her sons.
Her sons were 5 years old and the daughter was 7 years old. Her sons were not very bright but with her help they could gain enough strength to contend for the throne.
But for the time being her only aim, was to make sure that Samuels whereabouts are not found by the king so that her plan can succeed. That's why she had her family change the appearance of Samuel to make him hard to recognise.
She was also planning on getting baron mule on her side in case she ever needs to do something about Samuel. He had complete reign over underworld of the hamshire city.
She knew that the only ones who can foil her plan were the assassins so she planned on killing them when they return to the royal city for their reward.