Cut to Horatio charging down the hall as (Y)Elena tells him they've located Robin Kaye, and she's on a field trip to the aquarium with her classmates. No doubt Stewart has figured this out using his special child-molester senses. He's even had time to whip up an aquarium-employee uniform.
And then we all stop to admire the mermaids gamboling in the azure depths of aquarium, since it's obvious this episode has moved from any world grounded in reality and headed straight for a magical land far away. Look for Calleigh to ride by on her special friend Hawthorne The Unicorne, who is her slave, who she also loves. And then Speedle will show up in a suit of armor and fight an enchanted dragon, and Delko will trip along wielding his magic sword. I mean -- come on! In the time it took this clown to find out about the field trip and whip up a uniform, he could have driven that RV to a country which doesn't extradite American felons.
Anyway, yes, Stewart is in uniform at the aquarium and stalking Robin. He then turns around and notices Horatio watching him. Horatio's not actually moving to apprehend him or anything, electing instead to just glower. No doubt there's supposed to be some predator/prey thing based on the attention the camera just paid to the shark in the tank, but things are already short-circuiting in my brain from the logical conundrums this episode has presented, and so all I can do is watch as Stewart registers Horatio, then notices (Y)Elena on the other side of his escape route. So he does the predictable: picks up a kid as a hostage and makes for a balcony, all the better to have a dramatic confrontation with Horatio.
Stewart runs up some stairs -- hard to do with a kid under one arm -- and reaches said balcony. Horatio pops up to helpfully point out, "No way out, Stewart. Let her go." Stewart threatens to kill the girl, which does nothing to increase his leverage with Horatio. Horatio tells him, "I'm not going to ask you again. Let her go." Stewart replies, "I love them. I can't do without them." Horatio fails to come around to Stewart's point of view. Just as Stewart makes to throw Robyn off the balcony, Horatio shoots him with such force that Stewart goes rocketing over the edge instead.