It features a band of time travelling agents, working for the US Government, initially in an effort to investigate Mother Russia's sudden rise in technology. After they start encountering alien technology, it includes space travel adventures as well as time travel adventures (including traveling to other planets and then visiting their pasts). It evolves into a book series featuring myth arcs, intrepid merchants, and exploring ancient civilizations, both human and alien.
The books are:
- The Time Traders (1958)
- Galactic Derelict (1959)
- The Defiant Agents (1962)
- Key Out Of Time (1963)
- Firehand (1994, with P.M. Griffin)
- Echoes in Time (1999, with Sherwood Smith)
- Atlantis Endgame (2002, with Sherwood Smith)
The series contains examples of:
- Aborted Arc: Due to
Died During Production, the overarching Myth Arc that the series was building up will never be complete. - Advanced Ancient Acropolis:
- The first planet the group lands on in Galactic Derelict. It is a large, possibly planetwide city, but it is mostly in ruins and abandoned.
- Again, for the last planet they land on in Galactic Derelict, before their return trip home. What are the remains of an ancient spaceport with obvious signs of technology, and multiple cultures, but only remains of cultures and sentient creatures, until Echoes in Time, when they go back to its past, and revealed to be a highly integrated society with multiple sentient beings and tight-knit, evolved culture.
- Archaeological Arms Race: The whole thing begins with the United States and the Soviet Union racing to uncover lost alien technology.
- Auto-Doc: One of the devices on an alien ship is a cradle filled with a healing jelly. Spending time in the jelly quickly cures all wounds you've taken.
- Blind Jump: Alien spacecraft are controlled on interstellar journeys by carefully plotted courses recorded on tapes. If you can't read the label on the tape, or somebody switched it, you have no idea where you're going ... but it will get you there flawlessly. Whether you've got any way to get back — if, for instance, you used up your fuel — is another matter.
- Due to the Dead: A prehistoric tribe is set to cremate their chief with great honor. Too great: they intend to kill Ross Murdock on it as a sacrifice.
- Escape Pod: Ross Murdock fell into one (in a crashed alien ship) while dying of exposure to Arctic conditions. The lifeboat's automatic systems recognized him as an injured intelligent lifeform and tucked him into a bunk full of some sort of healing goo; he came out some hours later feeling fine.
- Gangsta Style: Alas, Firehand had the time travel project's weapons trainer, no less, use this technique (in a flashback) — in fact, it was presented as one of the clues telling the main character early on that this trainer knew her stuff. Ouch.
- Ghost Planet: The "pit-stop" planet and alien spaceport in Galactic Derelict. The home planet of the alien spacecraft is still inhabited by two primitive alien tribes who are at war, but it is made clear that they are not the civilization that built the ruined city they dwell in.
- Human Sacrifice: A prehistoric tribe is set to cremate their chief with great honor. Too great: they intend to kill Ross Murdock on it as a sacrifice.
- Imported Alien Phlebotinum: The humans discover the alien spaceships and their corresponding datatapes, but are never fully understood.
- In Harm's Way: The U.S. time-travel operation recruited a lot of these sort of people—"the expendable man who lives on action"—who had been "pressured by the peaceful environment into becoming a criminal or a misfit." They were sent back into some very un-peaceful history.
- Intrepid Merchant: The group was this during their expedition to the past in the first book, hence the title; merchants can go anywhere and no one would blink.
- Lost Technology: Scattered nicely throughout the series, especially on other, alien, planets.
- Make the Bear Angry Again: The Soviet Union from the 1958 version was retconned so that now "Greater Russia" is the antagonist faction. Furthermore, the description of the latter as having emerged from the ashes of the fallen USSR implies that post-Soviet Russia had reintegrated (diplomatically or by force) the rest of the post-Soviet states.
- Medieval Morons: One male lead tells the other that the 'primitives' they meet with in pre-history may be able to deduce scientific or mechanical principles from a rifle or other item, and therefore everything the Time Traders take with them to the past must fit the era, even to the point of disguising antibiotics in the form of local medicines. But most of the past folk we actually see do not come across as very intelligent, even the two characters, one a priestess and the other a chief's wife, who are interested in learning about the world beyond their doorstep.
- Myth Arc: The series enemies, the Baldies, and their involvement with humanity, are built up over the series.
- No Equal-Opportunity Time Travel: Inverted. Both the US agents and their Soviet counterparts are sent on undercover missions in different areas and eras of history (and their cover identities composed) specifically on the basis of their racial makeup. Not only is conspicuous behavior avoided for fear of the usual Butterfly of Doom, but because word of it in history books would alert the enemy to your position in time.
- Post-Soviet Reunion: Originally, the first novel was published in 1958, shortly after the Cold War had begun, and was set at the "end of the 20th century." When it was reprinted after the end of the Cold War, it included a new paragraph describing the emergence of a belligerent "Greater Russia" from the ruins of the old Soviet Union, to explain why the Russians were the enemy in a story set after the dissolution of the USSR.
- Scars Are Forever: Ross Murdock's burn-scarred left hand, the result of an encounter with the Baldies. On one planet, he is known as "Firehand" (and features prominently in the eponymous book).
- Space Police: There's speculation that the alien "Baldies" are this — at one point, the heroes wonder whether a video they found is the record of an actual case or the equivalent of a television "cop show".
- Time-Travelers Are Spies: The Russian and American agents both go back in time to find out what the others are doing in the past.
- Trading Bars for Stripes: Ross Murdock is recruited from prison.
- You Can't Go Home Again: In Echoes in Time, this is the fate of some human time travelers who go back into the far past on another planet. The rescue mission sent to retrieve them learns that the team survived, but were physically changed so that they could not survive returning to Earth, so they had made the best of a bad situation.
