In the film In the Shadow of the Moon, Rya, the time-traveling assassin, injects her victims with a substance which triggers their deaths at a later time. One of the victims happens to be driving a bus at the time of her death, causing significant collateral damage.

If the goal is to kill the victims, and she can get close enough to inject something in their necks, why not just... kill them? Why go to the trouble of injecting them with a substance that results in their deaths later?

Eventually, we find out that

the deaths are triggered from the future,

but it still isn't revealed why this is important or necessary.

  • My take was that all the deaths need to all happen at the same time, relatively speaking (e.g. within a minute or two of pressing the button that triggers them in the future) or else the timeline will change and the Rya won't know who to attack or when. This way she can inject people in a bunch of different time periods, but their deaths will all happen at the same time (sort of)
    – Valorum
    Aug 8, 2021 at 20:50
  • @Valorum that kind of makes sense, except that the last victim in 1988 doesn't die until long enough after the others that the police are able to find and question her, and compare her wounds to those of the previous victims.
    – LShaver
    Aug 9, 2021 at 20:59
  • 1
    Hence why I've posted as a comment, not an answer. It's not a particularly well-written film and it's riddled with plot holes.
    – Valorum
    Aug 9, 2021 at 21:01

1 Answer 1


James Blish wrote a story "Beep", Galaxy, Feb. 1954, and eapanded it into a novel The Quincunx of Time, 1973, about an organization which sends and receives messages into the past and the future, and operations to ensure that everyevent mentioned actually happens.

And one of the main rules of the organization is never mention the death of an intelligent being in any of thos messages. If they mentionedthe deaths of individuals in time messages, they might turn into an organization of assassins making certain that each mentioned death happens when, where, and how it did in the messages.

So possibly the organziation that Rya belongs does carry out assassinations in order to ensure that historically recorded deaths happen when, where, and how they are recorded to have happened.

"It is an ill wind that blows no good", and conversely "a good wind that blows no ill".

My ancestor William Lowman died during the yellow feaver epidemic in PHiladelphia, PA. in 1793, and his son-in-law Johannes Jauch also died it it, leaving a widow and three children. The widow, Eva lowman Jauch, married Henry Hurst in 1800, and had children, including a daughter Anne Frances Veronica Hurst in 1801. They moved to Lancaster, and Anne Frances Veronica Hurst married Jacob Demuth (1779-1842) in 1822, and had nine children, including my great great grandfather Henry Cornelius Demuth (1830-1906).

So I am descended from the second marriage of a woman widowed by the yellow fever epidemic. If that disaster hadn't happened I, and many of my relatives, would never have been born.

And it is possible that the leaders who send Rya to assassinate people in the past are descended from the second marriages of the widows or widowers of the people she assassinates, and send her so that they will be born.

Suppose that Rya is sent by leaders who don't live just a few centuries after the people they make her assassinate, but ten thousand years or more in the future. What possible interest could they have in whether specific persons die so many millennia earier?

Did you every hear of the most recent common ancestor, or MCRA, of a group of organisms.

In biology and genealogy, the most recent common ancestor (MRCA), last common ancestor (LCA), or concestor[note 1] of a set of organisms is the most recent individual from which all the organisms of the set are descended. The term is also used in reference to the ancestry of groups of genes (haplotypes) rather than organisms.

The age of the MRCA of all living humans is unknown. It is necessarily younger than the age of either the matrilinear or the patrilinear MRCA, both of which have an estimated age of between roughly 100,000 and 200,000 years ago.[14]

A mathematical, but non-genealogical study by mathematicians Joseph T. Chang, Douglas Rohde and Steve Olson calculated that the MRCA lived remarkably recently, possibly as recently as 300 BCE. This model took into account that people do not truly mate randomly, but that, particularly in the past, people almost always mated with people who lived nearby, and usually with people who lived in their own town or village. It would have been especially rare to mate with somebody who lived in another country. However, Chang et al. found that a rare person who mates with a person far away will in time connect the worldwide family tree, and that no population is truly completely isolated.[note 4]

The MRCA is the most recent common ancestor shared by all individuals in the population under consideration. This MRCA may well have contemporaries who are also ancestral to some but not all of the extant population. The identical ancestors point is a point in the past more remote than the MRCA at which time there are no longer organisms which are ancestral to some but not all of the modern population. Due to pedigree collapse, modern individuals may still exhibit clustering, due to vastly different contributions from each of ancestral population.[15]


In genetic genealogy, the identical ancestors point (IAP), or all common ancestors (ACA) point, or genetic isopoint, is the most recent point in a given population's past such that each individual alive at this point either has no living descendants, or is the ancestor of every individual alive in the present. This point lies further in the past than the population's most recent common ancestor (MRCA).

Eventually the point is reached where all people in the past population fall into one of two categories: they are common ancestors, with at least one line of descent to everyone living today, or, they are the ancestors of no one alive today, because their lines of descent are completely extinct on every branch. This point in time is termed the 'identical ancestors point'.

The identical ancestors point for Homo sapiens has been the subject of debate. In 2004, Rohde, Olson and Chang showed through simulations that the Identical Ancestors Point for all humans is surprisingly recent, on the order of 5,000-15,000 years ago. Ralph and Coop (2013), considering the European population and working from genetics, came to similar conclusions for the recent common ancestry of Europeans.[2][3][4]


In the Star Wars galacy people sometimes move from their home planet to another planet setteled by their species and marry and have children there. Thus the population of a space travelling species will not become totally isolated on differnt worlds but will become mixed so that a person will be descended from people who lved on all of the planets settled by his species 5,000 or 10,000 years earlier.

Suppose that a million years after Star Wars: Episode IV A New Hope some Star Wars "human" is sent back in time to ensure that Alderaan is exploded at the right date. And suppose instead that they blow up Alderaan a thousand years before or after the right time, figuring that such a small difference won't matter.

They will instantly vanish from existence, and so will all of the Star Wars humans born more than a few millennia after Alderaan was historically exploded, replaced by an entirely different Star Wars "human" population.

So if the people who send Rya into the past to assassinate people live more than 10,000 years in the future, they may believe that unless those persons died when they are recorded to have died, everyone in their future will never have been born.

Which organisms have the most effect on who long individual humans live? Microorganisms.

And each human contains millions, biollions, and trillions of microorganisms of many different species. And each human is constantly acquiring new microorganisms from their environment, and constantly leaving other microorganisms in their environment, mixing them up. With their short generations, microorganisms evolve very rapidly into new forms, most of them harmless, but some being deadly diseases which can cause humans to die.

So causing somone to die in a different place, or to die a day - or even an hour - earlier or later, would have the same effect on populations of microorganisms that exploding Alderaan a thousand years earlier or later would have on the population ofStar Wars "humans". And such a change in the populations of microorganisms will eventually result in a similar change in the population of humans.

So this my guess at a logical and rational reason for Rya to assassinate people with great care to ensure they die at exact specific times, places and circumstancees.

Of course there is no guarantee that the makers of In the Shadow of the Moon had such a rational reason for Rya's murders.

[1]https://en.wikipedia.org/wiki/Most_recent_common_ancestor#TMRCA_of_all_living_humans [2]: https://en.wikipedia.org/wiki/Identical_ancestors_point

  • 1
    I really can't make head nor tails of this answer. There's a lot of it that seems to be entirely irrelevant and the bits that are relevant don't seem to answer the question being asked.
    – Valorum
    Aug 8, 2021 at 19:47

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