After spending 15 years in the Oregon State Psychiatric Hospital, Cassidy (Natasha Henstridge - Against the Wild) has been declared safe enough to be allowed to leave and live a normal life. But the first thing on Cassidy's agenda is to pay her sister, Jane (Kelly Rutherford - No Greater Love), a visit as Jane has been raising her daughter, Emily (Peyton List - The Dog Who Saved the Holidays), as her own ever since she was committed for being criminally insane. Cassidy's return unsettles Jane and her attempts to warn people about Cassidy being insane appear to fall on death ears forcing Jane to take matters in to her own hands.
The law of casting can make or break a movie, take "A Sister's Nightmare" where we have Natasha Henstridge in the role of Cassidy, who has been in an institution for the criminally insane. Now when it comes to TV movies Natasha Henstridge often plays the nice characters and to have her here cast seemingly in the role of someone with psychotic tendencies immediately raises your suspicions that all is not as it may appear. Thankfully Henstridge is so good at playing it icy cool that as the story develops you are not entirely sure whether she is unhinged and a threat or whether maybe she has been wronged.
That brings me on to the mystery of "A Sister's Nightmare" and there are a few things going on. We get hints of some tragic event which lead to Cassidy ending up in a mental hospital. We have Jane hell bent on stopping Cassidy from bonding with Emily, who, whilst we are not told immediately, is clearly Cassidy's daughter. For something a little different there is Emily's phobia of water. And on top of this we have no one believing Jane when she tells them that Cassidy is still a danger. What is that danger and what is Jane really hiding other than Emily really being Cassidy's daughter? It is because of all this that even though you know that "A Sister's Nightmare" will end up with danger and a face off you are not entirely sure which way this will play out or at least not immediately.
Aside from that it has to be said that director Vic Sarin constantly uses Natasha Henstridge's looks, and by looks I mean her piercing eyes, as often as he can. And to be honest it works as scenes of her staring with the cold look of vengeance gives "A Sister's Nightmare" a nice slice of chilling.
What this all boils down to is that "A Sister's Nightmare" is in truth just an ordinary Lifetime movie. But it works what it has well so that whilst you can spot the plot points you are not entirely sure which way things will go when the big ending comes.