When Scully is getting William out of the car around 8:30 mark, there are two things wrong with how William is placed in the car. 1) William should be placed in the middle of the backseat, 2) he should be facing the back of the car and not the front. This is a legal requirement and Scully being a law enforcement officer should know this.
When Scully is talking on the phone to the shadow man in front of the internet café, you can see Gillian's Sanskrit tattoo on the inside of her right wrist.
Near the end when Scully drives out to the mine and gets out and sees the super soldier slowly walking near her, why doesn't she just drive away instead of running away from him on foot?
Shadow Man: You've had quite an earful.
Scully: Who is this?
(We see the Shadow Man at his desk)
Shadow Man: As my associate indiscreetly told you, we don't have names.
Scully: You've been listening to us?
Shadow Man: It's all I could do after you closed the shades, Agent Scully.
Scully: You ever heard of the Constitution?
Shadow Man: Yes. It's what allows foreign terrorists to live here and enjoy the American dream, until time comes to destroy it. But my trespasses are the least of your concern, after what they've done to you and Mulder.
Scully: What have they done?
Shadow Man: Actually, it's what they're prepared to do next.
Shadow Man: I'd be happy to tell Agent Mulder.
Scully: Well, you're going to have to tell me 'cause i don't know how to reach Agent Mulder.
Shadow Man: You reached him yesterday. You sent him an e-mail. Would you like me to read it to you?
Scully: Look why should i trust you? You're just a voice on the end of the phone. I'm not going to give you anything unless i can meet you. Unless I ... unless i can see your face. Are you still there?
Shadow Man: If you think you can flush me out you're making a big mistake. Bus bench, Internet cafe. Come alone. You have 20 minutes.
Doggett: How long are you going to do this?
Scully: Do what, Agent Doggett?
Doggett: Refuse to trust me ... or anybody. How else you going to get him home?
(Scully is in the internet cafe, typing an email to Mulder.)
Scully: (voiceover) I hold no hope you can respond to this. Or that it reaches you. I only hope that you are alive. I cannot help believing that you jumped off that train because you knew what I now know that these "super soldiers" if that's what they are, can in fact be destroyed. That the key to their destruction lies in the iron compound at that quarry. I am scared for you, Mulder. And for William. The forces against us are unrelenting. But so is my determination. To see you again. To regain the comfort and safety we shared for so brief a time.Until then, I remain forever yours... Dana
Shadowman: Your size? I know your blood type, your resting heart rate your childhood fear of clowns. I know the name of your college boyfriend, your true hair color, your ATM pin number, favorite charities, pet peeves. I know you spend too much time alone. And I know ... that on one lonely night you invited Mulder to your bed.
Scully: (Hoarsely) Oh, my God.
Shadowman: I was as surprised as you are.
Shadow Man: Mulder must die. Mulder or your son.
Terry O'Quinn (Shadow Man) is credited with "Special Guest Star" as well as being credited by his real name of Terrance Quinn.
The way the title of the episode is written - Trust No 1 also has a double meaning - Trust No One, and Trust Number 1, i.e. yourself above everything else. Given that everyone in the episode has to work out what's happening for themselves, this seems very fitting.
This is the third guest appearance Terry O'Quinn has made on The X-Files. He previously appeared in the season two episode Aubrey, and in the feature film Fight the Future. He plays a different character in each appearance.
The address for the Trust No 1 FANLISTING is:
Scully's screen-name is QUEEQUEG0925. Queequeq was Scully's dog in season 3, which was eaten in 'Quagmire'. 09/25 is the birthdate of Gillian Anderson's daughter, Piper.
This episode's tag line is changed to 'They're Watching'.
The 'Shadow Man' mentions that there are terrorists living secretly in the US, indicating this episode is set after September 11, 2001.
'Trust No One' were the last words of Deep Throat in season 1's 'The Erlenmeyer Flask' and also Mulder's computer password in 'Little Green Men'. During this episode Scully receives emails from Mulder with the address "Trust No 1".