"Nothing Ever Works Twice" is the first episode with a storyline featuring someone from Joe's past. In this case, a former flame looking for help in her efforts to obtain a divorce.
Some familiar tropes of the series begin appearing.
A client lies to Mannix.
Joe gets hit from behind and KO'd.
There's a car chase. This one involves a 1967 Mercury Colony Park, damaged by Mannix, but drivable.
Joe also goes off-roading in a four-door sedan.
Mannix uses a car phone (though not his).
There's a fist fight.
Joe lights up two cigarettes.
Body count of three.
Someone shows up in the end to help "clean up". In Season One it's usually Wickersham (Joe Campanella), in later seasons it's usually one of several police lieutenants.
As for the story itself, it's well-written enough to keep viewers interested. The only downside is by the time of the denouement, the killer is the only suspect left, there's no twist or surprise in the reveal.
Speaking of reveal, the George Barris customized 1967 Oldsmobile Toronado makes its first appearance in the series. A really sweet ride. Beats the heck out of those Mercury Comets.
Overall it's a strong episode, good action sequences, you get a glance into the past of Joe Mannix, and the Barris Toronado definitely raises the "cool factor" of our hero.