Using async.js with node.js

Visit.js - Notice that folloup.id refer to 0 or "n" Visits (like tree)

var visitSchema = new Schema({
  code : {type: String, trim: true, required: false, default: ""},
  Client : {
    id: {type: Schema.Types.ObjectId, ref: 'Client'},
  },
  attendant : [{
    name : {type: String, trim: true, required: false, default: ""},
  }],
  followup : [{ 
    id : {type: Schema.Types.ObjectId, ref: 'Visit'}
  }],
});

Client.js

var clientSchema = new Schema({
  name: {type: String, trim: true, required: false, default: ""}
});

So, I tried do that but it does not working. Why not?

Visit.find(function(err, visits) {
  var visitCards = new Array();
  async.eachSeries(visits, function(visit, callback) {
    var visitCard = new VisitCard();
    async.series([
      function(callback){
        Client.findById(visit.Client.id, function(err, client) {
          visitCard.client = client.name;
          callback();
        });
      },
      function(callback){
        visit.followup.forEach(function(followup){
          Client.findById(followup.Client.id, function(err, lfollowup) {
            var pfollowup = new visitCard.followup();  
            ...
            visitCard.followup.push(pFollowup);
            callback();
          });
        });
      }
    ],
    function(err, results){
      ...
      visitCards.push(visitCard);
    });
  },
  function(err){
    res.render('visits/index', { visitCards: visitCards});
  });
});

It seems that:

Client's callback return after "async.eachSeries(visits, function(visit, callback)" execute.

"visit.followup.forEach" finished before Client.findById execute.