ASP.NET MVC 4 return Json resulting in double json or empty data

I am getting either empty Json results or double json results and I don't know why yet?

base line: http://learn.knockoutjs.com/mail?folder=Inbox looks like this in chrome F12: {"id":"Inbox","mails":[{"id":1,......}

My Action:

public ActionResult Mail()
{
    string qs = "";
    foreach (var q in Request.QueryString)
    {

        qs += string.Format("{0}={1}&", q, Request.QueryString[q.ToString()]);
    }
    var proxyRequest = "http://learn.knockoutjs.com/mail?" + qs;
    var request = WebRequest.Create(proxyRequest);
    var response = (HttpWebResponse)request.GetResponse();



    var reader = new StreamReader(response.GetResponseStream());
    var str = reader.ReadToEnd();
    var data = Newtonsoft.Json.JsonConvert.DeserializeObject<dynamic>(str);

    //var json = JsonConvert.SerializeObject(data);  
        // Text Visualization looks good {"id":"Inbox","mails":[{"id":1,"from":"Abb....}
        // no outside quotes, no escaped quotes

        var res = Json(data, JsonRequestBehavior.AllowGet);
        return res;

}

So basically I am proxying the call, but the question is why is the result coming back as either not filled in or double jsoned.

using chrome network trace the result of the above looks like. [[[]],[[[[[]],[[]],[[]],[[]],[[]],...]

valid json, just empty.

when I change the code to look like this

var json = JsonConvert.SerializeObject(data);  
// Text Visualization looks good {"id":"Inbox","mails":[{"id":1,"from":"Abb....}
// no outside quotes, no escaped quotes

var res = Json(json, JsonRequestBehavior.AllowGet);
return res;

Chrome network trace has doubled jsoned the data. "{\"id\":\"Inbox\",\"mails\":[{\"id\":1,\"from\":\"Ab....}"

Since I don't know what the Json actually is, I did newton soft dynamic convert JsonConvert.DeserializeObject

That may be the problem behind my empty response?

Any help would really be appreciated. Thanks