While there isn't much information out there about episode 4 it does seem like it may be a 90 minute episode! On the AMC schedule they have Talking Dead starting 32 minutes later than normal. The only reason we could come up with it starting late is because the show was extended. We also believe episode 4 is either an entire Morgan flashback showing his journey or possibly flashbacks mixed in with his current story.
Source: www.amc.com/schedule