Setting Left And Right Node Values

I am getting errors when I try setting left and right values (which are String types) for my tree.I tried doing something like:

Node node = new Node("Is it human?", null, null);
node.getLeft().setNode("Is it Zelda?");//the first left Q
node.getRight().setNode("Is it Kirby?");//the first right Q

but that gives me a runtime error of "java.lang.NullPointerException" which points to the line 2. I also tried this:

Node node = new Node("Is it human?", null, null);
node.setLeft(setNode("Is it Zelda?"));//the first left Q
node.setRight(setNode("Is it Kirby?"));//the first right Q

but that gives me another error, pointing to the setNode for both lines 2 and 3,plus it wouldnt make sense since both setLeft and setRight takes in Node types, not String types.

Here is my Node class:

public class Node {
private Node leftPt, rightPt;//left and right pointers for Node
private String node, left, right;
public Node(String node, Node leftPt, Node rightPt){
this.node = node;
this.leftPt = leftPt;
this.rightPt = rightPt;

[code]....