The cold opening of the show delivered the big plot point of the show: mysterious murders. As the team investigates the murder, caused by an electrostatic impulse roughly twice as strong as a lighting bolt, they pick up another, similar event. Rushing to investigate the impulse, the team arrives moments too late to prevent another murder; however, they discover the two victims are linked: both were firefighters that were apart of the alien invasion of New York and it seems someone is out to get them. A quick cut away shows the cause of the murders: a Chitauri helmet which is generating some electrostatic energy.
While we are briefly led to believe that a fellow fire fighter is behind the murders, the team soon piece together the facts: the Chitauri helmet, which has been kept in the fire hall as a trophy, was infected with an alien virus and all those who have recently come into contact with it are dying. A third fireman dies as a result and the helmet is taken into S.H.I.E.L.D. custody to a place called "The Sandbox."
Once back aboard The Bus and in the midst of discovering the true nature of the alien virus, the show takes a turn for the dramatic. In an effort to remain spoiler free, I will just say that one of the agents has contracted the virus and, in the face of it being 3 for 3 in kills, things do not look good. Clearly, the devastation that Jeph Loeb teased in an earlier interview seems imminent. A conversation with Agent Blake, played again by Titus Welliver, who first assumed the role in the One Shot, Item 47, seems to add to the impending doom for the team.
It seems needless to say, but things shake out well for the team as it's far too early in the season to lose a member of the team, though they eventually will. The end of the episode does some exploration into the Coulson mystery and does some nice denouement for the episode, which can easily be considered one of the series' best. The show had some serious drama and continued to build some connections to the MCU proper. The last scene establishes something important going forward: Coulson, and his team, are evolving and they aren't going to lay down for anyone. Going forward the team is going to be a part of some big things and the show seems to be headed on the right path.
I've embedded the tweets of some fans of the show below; feel free to tweet @CBBrainSplatter
@CBBrainSplatter Heart pounding ......says the wife! the 9 yrd just said " level eight" sooooooo their hooked! Lol!!!
— the HULK (@CaptainHulk3) November 6, 2013