如何正确编写指针函数声明?

以下是我的代码,它导致以下错误:

错误:“Node::Node”指定构造函数,而不是类型

#include <iostream>

using namespace std;
class Node {
  public:
      int value;
      Node *right;
      Node *left;

      Node* find (int key);
};

Node::Node* find (int key)
{
    if (value == key)              { return this;}
    else if (value > key && right) { right->find(key); }
    else if (value < key && left)  { left->find(key); }
    else                           { return NULL;}
}

int main()
{
    Node *head  = new Node();
    Node *right = new Node ();
    Node *left  = new Node ();
    head->value  = 5;
    right->value = 3;
    left->value  = 9;

    head->right  = right;
    head->left   = left;

    Node *mm;

    mm = head->find(8);
    cout << mm->value <<endl;}

    return 0;
}