Plane is blocked all Raycast

I use Ray to find game characters, and a Coordinate Plane for moving these characters. But when the Plane is turned on, it blocks all Ray. There may be alternatives.

P.s. Sorry for English

 public class Grab : MonoBehaviour {
 
     public Plane plane;
     public LayerMask HitMaskChar;
     public LayerMask HitMaskClone;
     public Vector3 posPlane = new Vector3 (0f, 0f, -5f);
     public float distance = 10f;
 
     private bool isClone = false;
     private GameObject clone;
 
     // Use this for initialization
     void Start () {
         plane = new Plane (Vector3.back, posPlane);
     }
     
     // Update is called once per frame
     void Update () {
         CheckGrab ();
     }
 
     void CheckGrab () {
         Ray ray = Camera.main.ScreenPointToRay (Input.mousePosition);
         RaycastHit hit = new RaycastHit ();
         if (Physics.Raycast (ray, out hit, distance, HitMaskChar) && Input.GetMouseButtonDown (0)) {
             Debug.Log ("is work");
             if (!isClone) {
                 clone = CreatClone (hit.transform.gameObject);
                 clone.layer = 9;
             }
         } else if (Physics.Raycast (ray, out hit, distance, HitMaskClone)) {
             Grabing (ray);
         } else if (isClone) {
             DestroyClone ();
         }
     }
 
     GameObject CreatClone (GameObject Clone) {
         isClone = true;
         Clone  = Instantiate (Clone);
         return Clone;
     }
 
     void DestroyClone () {
         isClone = false;
         Destroy (clone);
 
         Debug.Log ("destroy");
     }
 
     void Grabing (Ray ray) {
         if (plane.Raycast (ray, out distance)) {
             clone.transform.position = new Vector3 (ray.GetPoint (distance).x, ray.GetPoint (distance).y - 2f, ray.GetPoint (distance).z);
        }
     }
 }