The question asks about epistemology and making truth claims in discursive social sciences (politics) and humanities (history). This is a methodological answer.
where is the best source to go to get a start-to-finish summary?
Multiple scholarly sources. Scholars are held to account by virtue of their scholarly reputation. One failure in method, interpretative validity, or conduct will ruin a career. This thread holds scholars to broad account, and they are closely held to account by peer review processes and revision of prior work. Scholars may not produce great material, but they produce epistemologically stable material due to their disciplinarity. Note that there will be multiple valid interpretations of most things; for two reasons. The first reason being, discursive accounts, story telling basically, end up with different stories based on the smallest divergence. If Fitzpatrick and Pirani both wrote the same thesis from the same sources, the subtle difference in their word choice level interpretations of Soviet life would be, effectively, different interpretations. On top of this, discursive field scholars do not retread the same sources, with the same theories and methods. They write different books. The second reason being, the evidentiary records contain within themselves multiple competing valid readings, they give rise to multiple as-yet undisproven theorisations, they can be read using multiple techniques.
Is there a stable, impartial, reliable site that can give me an overall summary of an event, with links to other articles that go into greater detail?
No, and there can't be for fundamental methodological reasons. Discursive knowledge isn't stable. New sources and techniques are uncovered, and there is no "reality lying behind" that confirms a thesis about a constant Universe. We only know our past or present through our knowing of the past or present. The past or present itself is untouchable. "The past" is an imaginary produced from records.
Impartiality is impossible, it is a partiality of its own kind (fallacy of moderation). Discursive statements regarding human conduct are fundamentally "normative," or moralistic, political or partial. All statements regarding human conduct will contain an explicit (ie: good, acknowledged) or implicit (ie: bad, concealed) theorisation of what humanity, society, the subject, personhood are.
The very concept of "events" is problematised in almost all mainline contemporary historiographies; though this is more of a theoretical debate over the relative causative merits of processes versus nexuses. The commonplace "event" usually isn't.
Finally, summary knowledge obscures all of the complexity of the above behind narratives designed to fit (at best) "lies for children" requirements, and at worst deliberate falsifications to serve an active social interest. (As opposed, obviously, to the necessary theoretical interpretations required by any account of social reality, and done solely in order to account for empirical evidence in the best possible unfalsified manner.)
Wikipedia, for example, has agreed that it serve NPOV: to portray all major accepted accounts of a subject with appropriate weight; as an explicit theorisation of "knowledge" in an encyclopaedic sense. Wikipedia regularly fails at this, even in best cases, as good faith editors disagree on the weighting of major accepted accounts. But Wikipedia's encyclopaedic purpose introduces a weighting that differs form the scholarly account; Wikipedia's weighting and presentation of a topic follows a "lie for children" approach to prepare people to start reading scholarly accounts.
With all that said, the best way to proceed is by reading encyclopaedia accounts, and then following up with the highest level critical surveys available in scholarship that are cited by the encyclopaedic account. In historiography this is the "Review Article," similar kinds of article exist in political science. From the review article you can identify subsequent works that are "worthy" to read.
For example, if I had an interest in the 1932-1933 Soviet famine, I certainly would not stop at wikipedia's articles on the Holodomor and the 1932-1933 Soviet famine. I'd draw up a reading list, then start searching Google Scholar for high level review articles on the topic, identify the major strands of thought, and read a number of well received works from different strands of thought.
And, as I noted above, Scholarship isn't perfect: it produces highly stable accounts, that are subject to ruthless partisan contestation and so will not be invalid due to partiality, and scholars inspect each other's work for methodological validity with regularity. This seems to make it the "least worst" and most comprehensive system of knowledge available.
In the mean time, before scholars get to work, I'd suggest you identify news sources who have a reputation for accuracy and sensitive awareness of partiality. Personally I like a combination of BBC, Al Jazeera, SBS (Australia) and the Guardian. Though through having identified the deficiencies of other sources, I feel confident I can read from lesser news outlets and understand the underlying situation despite the corruptions I feel these lesser outlets introduce.