I guessed that Barnes was out to get a cure for his son, as soon as it was clear that he was interested in the woman who survived his germ attack in the courtroom. Spreading an almost instantly deadly illness - a hyped up version of what is afflicting his son - is a bit extreme, but makes good epidemiological sense.
Less understandable is why Lizzie killed him, rather than letting Barnes inject his son with the possible cure. We saw at the end that she agonized about this decision, but for my money, not quite enough. But ethical quandaries and disagreement over decisions make for good television. And it was good to see Robert Sean Leonard aka House's Wilson in the lead villainous role, and a nice couplet with the slightly deranged by good scientist he played on Revolution last year.
The show is still dancing around on whether Red is really Liz's father, and the coming attractions promise more of this. As I've indicated several times, it will almost be counter-climactic when we find out that he is, which makes me think that he isn't. But if not, then what exactly is his relationship to Elizabeth?
And husband is still a question mark, which makes Elizabeth's lovey-doveying him disquieting. All in all, The Blacklist is probably the edgiest show on television right now, with James Spader the perfect persona to carry this forward.
See also The Blacklist Debuts: Alias Meets Jay Z ... The Blacklist 1.2: Mysteries ... The Blacklist 1.3: Construction Site Heights ... The Blacklist 1.6: Truth and Enigma