Throwing error back to main thread

[AgentSmith]

If I create a STA thread to do work, but an error occurs, how do I propagate the error back to the calling thread?

private void Form1_Load(object sender, System.EventArgs e)
{
    Thread t = new Thread(new ThreadStart(ThreadProc));
    t.ApartmentState = ApartmentState.STA;
    t.Start();
    t.Join();
    MessageBox.Show("Done");
    Application.Exit();
}

private void ThreadProc()
{
    try
    {
        throw new Exception("Test Bomb");
    }
    catch (Exception ex)
    {
        // Rethrow error to calling thread
    }
}