Json query result not getting set - json

Question

I am trying to use a Json request to get data from a login screen. But no matter if the login request is valid or not, I am always getting returned to my home screen. I think I am checking the result incorrectly?
Basically, in my Twitter-Bootstrap enabled site, I have a modal popup that takes the user to a login form.
The values are passed via a json query, to my MVC4 controller. A breakpoint shows I am getting good data.
Here's the scrip that sends the data:
<script type="text/javascript">
$(document).ready(function () {
$('.btnSubmit').on('click', function () {
var data = { username: $('.txtUsername').val(), password: $('.txtPassword').val(), rememberMe: $('.cbRemember').val() };
$.ajax({
url: '#Url.Action("LoginUser", "User")',
type: "POST",
contentType: "application/json",
data: JSON.stringify(data),
cache: false,
async: true,
success: function (result) {
if (result['success'] == 'true') {
alert("true");
window.location = '#Url.Action("Index", "Home")';
} else {
alert("BAD");
}
},
error: function () {
alert("Error in input");
}
});
});
});
</script>
And here is the controller method:
[HttpPost]
public JsonResult LoginUser(string username, string password, string rememberMe)
{
string success = "false";
string message = "Not set";
if (username == string.Empty || password == string.Empty)
{
success = "false";
message = "Invalid Username/Password";
}
else
{
if (ModelState.IsValid)
{
var us = new UserService();
var reply = us.Authenticate(username, Security.EncryptText(password));
if (reply == 0)
{
success = "false";
message = "Invalid Username/Password";
}
if (reply != 0)
{
var p = us.GetPerson(reply);
FormsAuthentication.SetAuthCookie(p.Id.ToString(CultureInfo.InvariantCulture), rememberMe == "on");
Session["UserDisplay"] = string.Format("{0} {1} - ({2})", p.Firstname, p.Surname, p.Email);
success = "true";
message = "Login Success";
}
}
}
var result = new { Success = success, Message = message };
var r = new JsonResult
{
Data = result
};
return r;
}
However, I always get the 'BAD' alert. Never the 'true'.
Can I check the result the way I am? Am I attempting to do this the right way? Basically, if I get 'BAD', I don't want the screen to refresh. Infact, I will want to show a message saying what ever is in the 'message' parameter.
Edit: I think 'result' is NULL.