Object Disappears on Start

I have a Zombie that is in front of my first person controller. I have a C# script attached to him that is supposed to be a wandering AI script. It makes the character walk in a random direction with a walking animation(walk01) then pause for a few seconds using an idle animation(idle), then repeat. However, when I start the game he just disappears. He is nowhere on the map, he is just gone. Here is the script:

 using UnityEngine;
 using System.Collections;
 
 public class WanderBehavior : MonoBehaviour
 {
     private enum WanderingState { Moving = 0, Pausing = 1 }
 
     public float wanderRadius = 8.0f;
     public float wanderPauseTimeMin = 2.0f;
     public float wanderPauseTimeMax = 6.0f;
     public float speed = 2.0f;
     public AnimationClip wanderWalkAnimation;
     public AnimationClip[] wanderIdleAnimationList;
 
     private Vector3 basePosition;
     private Vector3 currentDestination;
     private WanderingState currentState;
     private float pauseTimeout;
 
     void Start()
     {
         basePosition = transform.position;
         ChooseNextDestination();
         currentState = WanderingState.Moving;
         animation.Play(wanderWalkAnimation.name);
     }
 
     void ChooseNextDestination()
     {
         Vector2 randOffset = Random.insideUnitCircle * wanderRadius;
         currentDestination = basePosition + new Vector3(randOffset.x, transform.position.y, randOffset.y);
     }
 
     void PlayRandomIdleAnimation()
     {
         animation.CrossFade(wanderIdleAnimationList[Random.Range(0, wanderIdleAnimationList.GetLength(0))].name, 0.2f);
     }
 
     void Update()
     {
         Debug.DrawLine(transform.position, currentDestination, Color.white);
 
         if (currentState == WanderingState.Pausing)
         {
             pauseTimeout -= Time.deltaTime;
             if (pauseTimeout <= 0.0f)
             {
                 ChooseNextDestination();
                 currentState = WanderingState.Moving;
                 animation.CrossFade(wanderWalkAnimation.name, 0.2f);
             }
             return;
         }
         else if (currentState == WanderingState.Moving)
         {
             currentDestination = new Vector3(currentDestination.x, transform.position.y, currentDestination.z);
             transform.forward = currentDestination - transform.position;
             transform.Translate(Vector3.forward * speed * Time.deltaTime);
 
             if ((currentDestination - transform.position).magnitude < 0.1f)
             {
                 pauseTimeout = Random.Range(wanderPauseTimeMin, wanderPauseTimeMax);
                 currentState = WanderingState.Pausing;
                 PlayRandomIdleAnimation();                
             }
         }
     }
 
     void LateUpdate()
     {
         transform.position = new Vector3(transform.position.x, Terrain.activeTerrain.SampleHeight(transform.position), transform.position.z);
     }
 }

If anyone can help i would be very greatful because i really want to finish this game! Thank you!