Obviously, spoilers.
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The scene shows Arthur ordering his useless guards to search the castle for the umpteenth time for Merlin. The chief of the guards bursts into Gaius' chambers and asks about the whereabous of Merlin, since the King has ordered Merlin's arrest. Gaius replies that Merlin is working for Arthur as he always does at that time of day. Merlin is seen in Arthur's (radically refurbished, enlarged and renovated) room fluffing his pillows (so cute!) before Arthur bolts in, shuts the door and warns Merlin that the King has ordered Merlin's arrest, on account of Lady Catrina accusing Merlin of stealing her seal. Merlin tries to convince Arthur that Catrina is a troll trying to set him up and Arthur is clearly torn, but urges Merlin to escape via a back door.
It seems that despite Arthur's unwillingness to believe that Catrina is a troll his non-jerk mode has returned in full force: he cares for Merlin and definitely does not want him to be thrown into the dungeons. Helping a convicted man to escape is tantamount to treason (not that Uther cares, since he's ensorcelled). Arthur looks at Merlin confusedly/yearningly as the latter escapes: he trusts Merlin and has a hard time trying to match his facts up (poor Arthur).
This is, all in all, very promising. Tomorrow's episode: Gaius wears green.