Axe Murderer (II) - S2.E26

Bobby works with the firm of Cage and Fish to help in the defense of Marie Hanson, an apparent axe murderer who may have been Lizzie Borden in a past life. Ellenor discovers that her new boyfriend is the crooked chiropractor treating Rebecca, while Lindsay and Helen discuss Helen's future with the DA's office.

The crossover starts on Ally McBeal S01E20 The Inmates (I).