CBS released the promo trailer for Hawai Five-0 episode 3.16 'Kekoa' guest starring Summer Glau, airing on Monday, February 11, 2013.
In this episode, Summer Glau plays Maggie Hoapili, a woman involved with an underground fighting ring who also happens to be searching for the person who murdered her father, a Lua (ancient Hawaiian hand-to-hand combat) master. And it looks like Maggie herself will get to fight.
Of course, the trailer is misleading you and one should not draw conclusions based on it.
As for your predictions on the future of the show, i completely disagree; the show had so-so ratings in its second season (last year) but this season rocks ratingswise. While H50 and Castle were neck to neck last season, H50 beats Castle regularly. Of course they suffer when NBC's hit show 'Revolution' is on air but networks have learned to include that data.
Contrarily to what happened with Syfy's Alphas, Summer glau is just a guest star among hundreds of other on H50 and isn't a major draw for the kind of audience who watches the show on CBS.
If this is true and they know that, then once again Summer has been used as a pawn to try and get more viewers. I see yet again that a reference to TSCC has been used when she is tied to the chair. Remember, she is in Hawaii.
This looks intense. I sure hope it leads to more exposure for Summer. Peter Weller was on the last episode playing a sniper who was out for revenge. He had prosthetic limbs which I suppose is a reference to his performance as Robocop.
Since H50 follows a "case of the week" format and since this promo trailer doesn't seem to refer to any recurring plot points, Summer Glau fans should be able to just tune in without having much background information.