this is "nightline." >> breaking news. u.s. forces on the attack. tonight, launching military air strikes against i.s.i.s. in syria. the mission, to degrade and destroy the brutal islamic terror group. fighter jets, bombers and tomahawk missiles, bearing down on i.s.i.s. strong holds. as a flood of refugees leave the region. we're there with the latest. and vanished. the desperate search for tanna graham continues. now, the man police say was with her last is gone, too. >> we want to talk to him. >> did they let him slip away? what we're learning tonight, as her parents beg for clues, to find their baby girl.

good evening. thanks for joining us. breaking news as we come on the air tonight. american forces on the attack. the first wave of u.s. air strikes hitting i.s.i.s. targets in syria, opening a new front in the battle against the islamic terror group. for the very latest, we turn to abc's chief global affairs correspondent, martha raddatz. >> reporter: juju, this is the biggest wave of air strikes we have seen in a single day since the u.s. began attacking

i.s.i.s. in early august. and we did not do it alone. five arab nations joining in the strike, which pounded some 20 targets in the area of raqqa. that's anúymp i.s.i.s. strongh and believed to be where the british and americans were executed. the air strikes carried out by u.s. stealth bombers and fighters, and tomahawk missiles launched from the sea. the f-22 raptor and expensive stealth fighter used for the first time in combat. the targets, i.s.i.s. safe havens. command and control and logistic centers. twitter, lit up with reports of huge explosions around raqqa. the other arab nations taking part, all largely sunni, including jordan, saudi arabia, bahrain, qatar, and the united arab emirates. the kind of coalition the u.s. has been trying to build to go after i.s.i.s. a big step as the u.s. expands

the fight against i.s.i.s. into syria, where the president was loathed to go for so long. but he gave the go ahead for these strikes. and throughout this evening, he has been briefed on the progress. tomorrow, he heads to new york and e u.n. we do expect to hear from him then. these air strikes will be ongoing. the chairman of the joint chiefs of staff says the fight against i.s.i.s. in syria will be persistent and sustainable, which means this will likely continue for months on end. juju? >> martha, thanks, as always. and joining me now, abc news chief investigative correspondent, brian ross, who has been tracking the growing terror threat. now, that u.s. air strikes are under way, what might this mean for i.s.i.s.? >> this is a ruthless group, whose members seem to enjoy their medieval barbarism. the air strikes led to

beheadings. i.s.i.s. escalated its threats to america, in anticipation of what happened tonight. as i.s.i.s. turned up the tempo on its propaganda machine today, with new videos of its military-like formations, and dire threats to american civilians, u.s. officials revealed details of a crackdown on westerners who want to join i.s.i.s. or already have, like these brittons, who appeared in a new video today. >> we are working closely with our international partners to mitigate this threat. >> reporter: u.s. officials said today, efforts to shut down the jihad pipeline to i.s.i.s., will focus on boston, minneapolis, and los angeles. cities that have already sent a number of young recruits to i.s.i.s. basic training. the kind of young men and women, seen in this latest video, parading in uniform, with brand-new ak-47s. the urgency of the coming white house push against i.s.i.s., was underscored today by one of the terror groups weekend propaganda

messages. its chief spokesperson earned supporters around the world. if you can kill a disbelieving american or european, especially the spiteful and filthy french, or an australian or a canadian, then rely upon allah and kill him however it may be. and i.s.i.s. followers posted this video, of a 55-year-old french citizen, they said they had kidnapped and would behead in 24 hours, unless the french stopped bombing of i.s.i.s. positions in iraq. as for i.s.i.s. itself, it is believed to be holding some 15 western hostages, including two, young americans, all of whom have been threatened with executions. juju? >> brian, is it possible that the air strikes cover for a possible rescue mission? >> reporter: >> that's possible. but u.s. authorities said if there was any chance, they would

try to mount a second attempt. they are looking for command and control centers. >> this is the first step in a major campaign. thanks for that update. we turn to alex marquardt, who spent the day talking with refugees, fleeing the threat of i.s.i.s. he's just across the border from syria and joins us from turkey, where there was a mass exodus under way even before tonight's air strikes. alex? >> reporter: good evening, juju. the past several days have seen i.s.i.s. pushing into northern syria, taking over predominantly kurdish towns. that's sent refugees across the border into turkey. the u.n. says 130,000 over the past 4 days. that's the biggest-single exodus of refugees since this war began over 3 1/2 years ago. we met many of the refugees who

told us, if they stayed behind, they would have been executed by i.s.i.s. they came with what little they could carry. and angrily told us that the u.s. is doing nothing to stop the i.s.i.s. advance. that is before these air strikes started. many of the refugees in turkey will be happy to see the air strikes carried out by the u.s. and the other countries. at the same time, it could set off a new wave of regees, fleeing from safety, from those areas where i.s.i.s. is operating. the u.n. and turkey, already preparing for many more refugees to cross the border. juju? >> alex, thanks. our thanks to alex marquardt, reporting from the region. stay tuned. abc news for all of the latest on these breaking developments. up next for us, the anguished parents of a missing college student, speak out as more than 1,000 volunteers join their urgent search. now, police are looking for the man last seen with her. what evidence do they have? and what does he know about her disappearance? ♪

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>> reporter: that's when police say he sped away in his car, and were tailing him, decided to let him go, that may have been on purpose. >> he may take you to a body, evidence, a weapon, whatever it might be, a secluded location. they panic. let him go, and see if he leads them to more evidence. >> reporter: this afternoon, they were back at his apartment. taking out bags to go back to a lab. >> they were going to see a number of things. are they armed with more information, about potentially what happened or could have happened? are there areas of his living quarters that didn't get adequately searched, items that

belong to her? it's all of the above. the real key in this case, obviously, is how can they link her disappearance to jesse. >> reporter: this isn't the first disappearance in virginia. the list of missing is long. so many cases, families crying out, just like the grahams. this year alone, 116 missing in virginia, all under 20 years old. >> i think the whole idea of holding somebody hostage for weeks, months or years, is probably not a realistic hope. it's happened. we've talked about these cases in the recent past. but it's not a common thing. when they disappear like this, and we don't hear anything for days, weeks or months, the p presumption is, something has happened to them. >> reporter: they've issued a warrant for reckless driving, but not for the disappearance. they warn the public, this is far from over. >> anyone out there in the community looking for hannah

graham to get tunnel vision because we have a name. >> reporter: friends and family are holding on to hope that this student, this daughter, will return. her parents speaking out for the first time this weekend. >> she's enormously precious to us all. somebody knows what happened to hannah. all we want to do now is to bring hannah home safely. and i appeal to anybody who knows anything, please, please, help us. >> reporter: for "nightline," i'm steve osunsami, in charlottesville, virginia. next up for us, move over, dogs. man just might have found a new best friend. we're revealing the secret message of cats and the message behind the meows. what they're trying to say, we ed her fever. you raise her spirits. we tackled your shoulder pain. you make him rookie of the year.

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okay. think about this. do cats have superpowers? can they save not only their own nine lives but yours, as well? my cat-loving co-anchor, dan harris, revealed surprising truths, to make sure you never think of your feline friends the same way again. >> reporter: as a dude who loves cats, i spend a lot of time defending myself against haters. but this new documentary from nat geo, called "the secret life of cats," provides me with useful ammunition. think cats are wussified? this cat may have saved her life. she left the stove on. the place would have exploded when the heating came on at 4:00

a.m. but he smelled trouble and woke his owner up. >> one of her claws. and i knew there was something wrong. he is my hero. ain't you, hey? >> reporter: think cats don't care about anybody other than themselves? this blind and partially deaf dog lived most of his life in dead, until he found a seeing-eye cat. >> he seemed to know there was a need there somehow. i don't think i've seen some get along as well as these two. they rely upon each other. >> here we are, with a compliant gus harris. his heears are back. nat geo sent this veterinarian to my apartment to meet my cat. once in a while, one of the cats will rub against me. i always thought that was a sign of affection. but it's actually not. >> it's saying, you're mine. i'm marking you. >> reporter: as the film explains, cats need to mark

everything and everyone with their scent so their world stays familiar to them. we're going into the closet. two out of three of my cats spent the interview hiding in the closet. why do they like being in little spaces? >> they like being secure. >> reporter: the documentary is filled with fascinating facts about cats i never knew, even though i lived with these creatures my entire life. why do cats do that thing when they give you an unsolicited massage from their paws? they have to knead their mom's belly to find their milk. when they find that to you, they're re-creating the comforts of kittenhood. and what are the whiskers for? they are sensitive navigation tools. even blind cats can find their way around, using whiskers the way people use a stick. and cats pretty much always land

on their feets. but nat geo used high-speed cameras to see how they do it. >> you'll see a cat in less than ten seconds. you realize, here's down. and they get the front end oriented correctly. and then, the back end. and extend their little legislation. get their paws out. when they hit the ground, they're not going to slip. arch their backs so they have the spring in their suspension system. okay, fine. survived that one. >> reporter: this cat, sugar, survived a fall from the 19th particular of an apartment in boston. >> this chipped teeth. no scratches. >> reporter: this film with all of its secrets and moving stories, may play its little part in eroding the p.r. problem facing cats. >> many times people think they're aloof. and they're really not. they're just a different species. a whole different animal. they are loving. once you get to know them.

they're not going to love like a dog. but they have great senses. when you bring them into a house, it's always for life. >> reporter: for "nightline," this is dan harris, in my apartment. >> i didn't think he could be more obsessed. "the secret life of cats" airs thursday, october 2nd, on nat geo wild. "world news now" is coming up soon, with the breaking developments of the air strikes against syria. and tune into "good morning america" tomorrow for a full report, as president obama travels to new york for the u.n. general assembly. thanks for watching abc news. good night, america. have a good night.

oh, come o on, ray. you're just going to sit here and wait for the cable to come back on? how long can it be out for? i mean, this is crazy. we've been 2 minutes. yeah. if your finger was stuck in a car door, would d you say it's only been 2 minutes? no. what? i like tv. now, look, why don't we just sit and d talk, hmm? why? what's wrong?

nothing's wrong. when was the last time that yound i just sat here and talked? the last time that something was wrong. all right, just forget it. look, debra, you know, i work all day. when i come home, i just-- i want to relax. and talking to me isn't relaxing, huh? ok, we'll talk. good. ahem... so go ahead. no. no. why? why? no, no, see, that's what you always do. you always say, "hey, let's talk," and then you throw it to me. no. you say, "let's talk," then you should have topics ready. i'm not good when i'm justt expected to talk. "expected to talk"? yeah, yeah. i'm good with regular talk, you knowlike, uh... "these pants are itchy," or... "hey, get down from there!" those things. but i'm just-- but this--