Posting it now while it's fresh in my head! 
Ep4 recap:
Lorna Bow/Delaney was arrested by the kings men for stabbing the duke of Richmond. They offered her to sign over her share of Nootka to the crown in return for escaping hanging for her crime. JD informed the EI company who intervened and realised the crown is acting in their own interests rather than the "common cause" they had previously discussed.
JDs spy in the EA company told him he won't be given a license to trade in Nootka.
JD watched a chemist and a married woman "conduct an experiment" but interrupted before there was an explosion.
JD hires the chemist to make gunpowder for him.
JD's horse has a sixth sense
JD is attacked by a large ugly bald man sent by the Americans who knocks him unconscious. JD comes round and slices parts off the ugly man, has a fumble in his guts and walks off. A small boy witnessed it.
JD receives an invite to a ball from a countess who uses her feminine wiles to improve her position in life. He also receives one from the Americans but I'm not sure what it's for.
JD attends the ball with his step mother. Suspect he had a bath! 
his sister is at the ball, it's a real family affair!
Meanwhile atticus and his bandbox of merry men break into the EI company to steal (I forget what) something to do with making gunpowder.
JD meets the countess who turns out to be Carlsbad.
Zilpha's repulsive husband challenges JD to a duel.