Crossing the Line is a 2004 science fiction novel by British writer Karen Traviss.

It is the second book of the Wess'Har Series.

[1] Its predecessor was called City of Pearl, published in February of the same year.

Some of the main characters include Shan Frankland, hardened copper now infected with c'naatat; Aras, the lonely Wess'har, outcast by his horrible disease; Eddie Michallat, journalist who finds himself in a position to affect history; and Lindsay Neville, the Marines Commander trying to deal with the loss of her newborn son David, and bent on revenge on Shan.

[2][3][4][5][6][7][8] The book concerns the struggle of Shan Frankland, a police officer in the year 2376, to cope with biological changes that have been made to her body by an alien species.