“Signal” is one of the most innovative and original thrillers I’ve ever had the privilege to watch. It captivates you right from the beginning and never lets up. The writing is crisp and taut, leaving the viewer to sit in wonder as to where the next leg of the story is going to go, while at the same time, wondering what the fate of our three protagonists is.

Park Hae Young is a brilliant criminal profiler with a tragic past, one in which he seems to be the center. While he’s a lieutenant with the police department, he does not like the police, nor does he have any faith in their ability to do their job—and with good reason as we find out as the story unfolds.

Detective Cha Soo Hyun is one of the few female violent crimes detectives who seems cold and a bit aloof, but she’s dedicated to her job, and she also comes with a tragic past: the only person to treat her with respect as well as the love of her life in Detective Lee Jae Han who mysteriously disappeared 15 years ago from when this story is set.

Finally, we have Detective Lee Jae Han who leads a one-man crusade to fight against police and political corruption within the police department. He has absolutely no compunction about acting alone, as he’s determined to always do the right thing and bring justice for those who are incapable of getting it otherwise. In many ways, Lee Jae Han is the glue of the trio, and demonstrates that you can never give up no matter what happens. He is the one person Park Hae Young respects within the police department, and soon Cha Soo Hyun as well.

The main focus of this series is a radio that sends its transmissions into the future, and always at the same time, although not every day. Park Hae Young is soon amazed that he’s speaking to Detective Lee Jae Han in the past, using a radio without batteries! How can this be? The series does not ask nor require an explanation, but simply for the viewer to go with it. Perhaps it is the spirit of Lee Jae Han and his fierce determination that causes this phenomenon to occur. In the end, it doesn’t really matter.

Soon placed on a Cold Case Squad under Cha Soo Hyun, Park Hae Young and Detective Lee Jae Han begin to tackle cold cases of the past, and together, hope to solve them and catch criminals who are uncaught—that is until the mysterious radio transmission begins to occur. Park Hae Young has access to evidence that Detective Lee Jae Han doesn’t in the past, including the future location of crimes at future points in time.

However, we soon learn that not everything is resolved because of this advantage, and Park Hae Young quickly discovers that certain things that have been corrected are not always for the best, as others are forced to pay a price for the interference.

There are plenty of plot twists as the story continues with the three of them trying to uncover the central plot to the story that has caused the death of Detective Lee in the past as well as the death of Park Hae Young’s brother. This, of course, raises certain questions, whether they be moral or ethical: can Detective Lee be saved from his fate? Should he be? And can anything be done to save Park Hae Young’s brother?

The series raises a glaring philosophical question: if you could go back and change something from the past, would you? Most people, without really thinking things through, might quickly say, “Yes!” But then, how would things change? This is something that our three characters must ask and answer within the scope of the story. Kobe Bryant was once asked if he had a time machine, would he not want to go back and change things? He very quickly said, “No. I’d never use it. Because that undermines everything that I ever learn from my mistakes.”

Most people have events of the past that they wish they could have done differently. These may even include tragic moments where accidents or events have led to the death of a loved one. Therefore, it may be far more challenging to refrain from using a time machine ability to change the past with the hope of changing the future.

Time stories are very, very difficult to do well. They tend to fall under one of two results: those done very well, and those that are done very badly. There really isn’t an in-between. This is not only one of the few that does it well, but it’s among the very best that I’ve seen. Perhaps only time stories in the Star Trek universe have been done better.

While all three actors are absolutely fantastic in this series, it’s Jo Jin Woong who is the standout for me. He carries himself beautifully as a dedicated detective who is very uncomfortable with personal advances, such as those we see from Cha Soo Hyun toward him, leading to some absolutely hilarious exchanges between the two of them. He plays a hard-nosed detective who refuses to take guff from anyone, no matter their rank. He’s definitely a very idealistic police officer who still believes in the system and that his job is to bring justice. In many ways, Detective Lee is a true hero.

This is a series that will hold your interest all the way to the end. I had only a slight reservation at the very end, and I thought it was because they might have been leaving the door open for another season, but that wasn’t the case. How did Detective Lee survive/escape his last attack? And are Park Hae Young and Cha Soo Hyun successful in, not only getting to him in time but also able to bring down the corrupt congressman? The answers to the last two questions, we can assume that they do, but the first question is left much more obscure that, frankly, needed an answer. But, neither of these prevented me from being grateful for being able to watch such a fantastic series!