The fourth season of The Americans continues some of the storylines from prior seasons (tying some of them up completely and shifting others) and introduces new storylines. The big new storyline involves bioweapons and brings in the great character actor Dylan Baker as another soviet living in the US and working as a biochemical scientist. The storyline with Martha, after Phillip revealed his real identity to her in the prior season, takes a prominent role this season and both he and Martha are in constant danger of being discovered by the FBI. Phillip and Elizabeth also have to deal with the fallout of Paige telling Pastor Tim about her parents, trying to figure out whether to kill him and risk alienating Paige further.
For those who get the DVD set, the A/V quality is definitely not as good as it could be, and one of those where the streaming quality (in HD) is better than what you get on the physical discs. The extras are very bare bones, just some deleted and extended scenes. There are no behind-the-scenes features or commentary tracks as there have been in prior seasons. So, this basically amounts to little more than an MOD set, and one of those series that Fox (which has heavily preferred steaming) only puts out a bare-bones set. So really, the only reason to get the DVDs is that you want to keep your collection current.
Overall, the season is very good. There are definitely twists and turns throughout the season, and the series ratches up the tension as Phillip and Elizabeth are always in danger of being caught. The cast is top-notch, not only the main cast but the supporting characters as well. Margo Martindale and Frank Langella are great as Philip and Elizabeth's handlers, and Julia Garner does a great job as Kimmy in her limited role. Matthew Rhys gives a standout performance this season playing Phillip as very conflicted and torn between being a good Soviet and an American becoming more and more disillusioned with his real job. There is a lot of violence and some sexual content as there has been in every season, although I would say that the sex is a bit toned down in this season. If you have been a fan of the series up to this point, it is definitely still worth watching. If you are looking for a new series to watch, start this at season one and enjoy.