This was episode fifteen of season three meaning we are about 3/4 of the way through its 22 episodes. It was also episode 62 of 82 meaning we are about three quarters of the way through all 4 seasons.
On island Kate wakes up in the woods handcuffed to Juliet and in their little adventure they are drenched in a downpour, have a wrestling match and fall into a mud puddle while avoiding the smoke monster not once, but twice. Loce has disappeared with the Others and in the end Jack, Kate ans Sayid are reunited and head back to the beach camp. Much to the chagrin of kate and Sayid, Jack insists the they take Juliet along.
The off island flashback shows Kate trying to contact her mother to find out why she turned her into the Feds. She gets unexpected help from another woman, who unbeknown to her was conned by Sawyer and is carrying his child. Unfortunately for Kate, mom loved her abusive husband, so when Kate thought she was protecting her from him by torching the house he lay passed out in, she was really hurting her.