Xcode won't open up ContentViewController but stays on the launch screen

I am trying to compile my Xcode application. It builds successfully however it doesn't get past the launch screen.

Also It keeps referring me to this particular line of code: instantiateViewControllerWithIdentifier (full code below) and in the logs I get this message:

"2015-05-09 21:36:20.376 banoffee[2104:430498] Unknown class ContentViewController in Interface Builder file. Could not cast value of type 'UIViewController' (0x10741f418) to 'HelloHi.ContentViewController' (0x1049aa2e0). (lldb) "

Can anyone please help me fix this?

import UIKit

class ViewController: UIViewController, UIPageViewControllerDataSource {

    var pageViewController: UIPageViewController!
    var pageTitles: NSArray!
    var pageImages: NSArray!

    override func viewDidLoad() {
        super.viewDidLoad()

        self.pageTitles = NSArray(objects: "Welcome", "Hello")
        self.pageImages = NSArray(objects: "page1", "page2")

        self.pageViewController = self.storyboard?.instantiateViewControllerWithIdentifier("PageViewController") as! UIPageViewController

        self.pageViewController.dataSource = self

        var startVC = self.viewControllerAtIndex(0) as ContentViewController
        var viewControllers = [startVC]

        self.pageViewController.setViewControllers(viewControllers, direction: .Forward, animated: true, completion: nil)

        self.pageViewController.view.frame = CGRectMake(0, 30, self.view.frame.width, self.view.frame.size.height - 60 )

        self.addChildViewController(self.pageViewController)
        self.view.addSubview(self.pageViewController.view)
        self.pageViewController.didMoveToParentViewController(self)

    }

    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
        // Dispose of any resources that can be recreated.
    }

    @IBAction func restartAction(sender: AnyObject) {

        var startVC = self.viewControllerAtIndex(0) as ContentViewController
        var viewControllers = [startVC]

        self.pageViewController.setViewControllers(viewControllers, direction: .Forward, animated: true, completion: nil)

    }

    func viewControllerAtIndex(index: Int) -> ContentViewController

    {

        if ((self.pageTitles.count == 0) || (index >= self.pageTitles.count))
        {
            return ContentViewController()
        }

        var vc: ContentViewController = self.storyboard?.instantiateViewControllerWithIdentifier("ContentViewController") as! ContentViewController

        vc.imageFile = self.pageImages[index] as! String
        vc.titleText = self.pageTitles[index] as! String
        vc.pageIndex = index

        return vc 


    }

    //MARK: - Page View Controller Data Source

    func pageViewController(pageViewController: UIPageViewController, viewControllerBeforeViewController viewController: UIViewController) -> UIViewController? {

        var vc = viewController as! ContentViewController
        var index = vc.pageIndex as Int

        if (index == 0 || index == NSNotFound)
        {
            return nil
        }

        index--
        return self.viewControllerAtIndex(index)

    }

    func pageViewController(pageViewController: UIPageViewController, viewControllerAfterViewController viewController: UIViewController) -> UIViewController? {

        var vc = viewController as! ContentViewController
        var index = vc.pageIndex as Int

        if (index == NSNotFound)
        {
            return nil
        }

        index++
        if (index == self.pageTitles.count)
        {
            return nil
        }

        return self.viewControllerAtIndex(index)

    }

    func presentationCountForPageViewController(pageViewController: UIPageViewController) -> Int {
        return self.pageTitles.count
    }

    func presentationIndexForPageViewController(pageViewController: UIPageViewController) -> Int {
        return 0
    }

}