[Lots of spoilers follow.]
First and foremost, David Rittenhouse, the founder of Rittenhouse, is revealed, during the American Revolution, and killed. He's played by someone who looks like Rudy Giuliani (Armin Shimerman of Star Trek fame, made up to look like Giuliani), which means he makes an apt-looking villain. His killing is tied up with Benedict Arnold, who's also killed, as is the British high-commander, Lord Cornwallis, who also had things to do a few decades in the future in his and our known history. But Timeless has already established its penchant for changing some major things in history - with no big effects in the future (2016) - that is, no big effects in our known present and history, but serious changes in the personal lives of our heroes.
Killing Rittenhouse, of course (also a real person, 1732-1796, by the way, a clock maker, Rittenhouse Square in Philadelphia was named after him - I hope none of his descendants take umbrage to his character in the series), won't eliminate Rittenhouse the organization. David says others are already part of the nefarious group, and then there's his son. In a great scene in the woods, Flynn can't quite bring himself to kill the son, but then he turns and levels his gun, and Lucy is shielding the boy. Flynn can't quite bring himself kill Lucy, either, and the son escapes. The scene harkens to the chestnut of a question in many time travel stories - if you had a chance to kill Hitler when he was still a young, innocent child, would you do it? Preventing his parents from ever meeting would be a less brutal, more ethical way of preventing Hitler's rise, but that option may not be available to the time traveler.
Meanwhile, in a touching scene in the future, Denise gives Lucy a thumb drive with Denise's family history in case something Lucy and company do in the past erases Denise's family, the way that something they did erased Lucy's sister. It's a memorable moment - which also raises the unspoken question of: what happens if something Lucy does in the past erases not Denise's family but Denise? The moment is also significant because it shows that Lucy, as a time traveler, not only possesses memories of people erased, but traces of them in the form of photos and videos can survive in her possession,
The final scene is good, too, with Flynn kidnapping Lucy - he said they'd be working together. See you back here with more reviews of the good and evil they do next year.
See also Timeless 1.1: Threading the Needle ... Timeless 1.2: Small Change, Big Payoffs ... Timeless 1.3: Judith Campbell ... Timeless 1.4: Skyfall and Weapon of Choice ... Timeless 1.5: and Quantum Leap ... Timeless 1.6: Watergate and Rittenhouse ... Timeless 1.7: Stranded! ... Timeless 1.8: Time and Space ... Timeless 1.9: The Kiss and The Key
a time-travel agency in Riverdale ....