Are things all well in the hive?

OK, got in from work today with the intention of opening up hive to see what is going on, but bees were really active, never seen them so busy, decided would leave the opening up until tomorrow.
Went out with kids for a tapas and when we got back had a quick check on bees, yes they are addictive! There was a large group of them moving about in entrance, more than I have ever seen, what's that all about, it's dark and the bees are still active, not flying but just so many in entrance? So many things go through your mind, are they about to swarm, they can't be, they were a nuc 9 days ago with this year's queen, not possible, or is it!
Oh well it's pitch black, not much I can do about it now, maybe a later start at work tomorrow and open hive first thing, see if I need to add a super.
It would be gutting for them to swarm this quickly, I thought I had a year before this hassle!
And I used to think that working was stressful! :-)